Sickle cell disease (SCD) is characterized by intermittent vaso-occlusive events and chronic hemolytic anemia. Vaso-occlusive events result in tissue ischemia leading to acute and chronic pain as well as organ damage that can affect any organ system, including the bones, spleen, liver, brain, lungs, kidneys, and joints. Dactylitis (pain and/or swelling of the hands or feet) is often the earliest manifestation of SCD. In children, the spleen can become engorged with blood cells in a "splenic sequestration." The spleen is particularly vulnerable to infarction and the majority of individuals with SCD who are not on hydroxyurea or transfusion therapy become functionally asplenic in early childhood, increasing their risk for certain types of bacterial infections, primarily encapsulated organisms. Acute chest syndrome (ACS) is a major cause of mortality in SCD. Chronic hemolysis can result in varying degrees of anemia, jaundice, cholelithiasis, and delayed growth and sexual maturation as well as activating pathways that contribute to the pathophysiology directly. Individuals with the highest rates of hemolysis are at higher risk for pulmonary artery hypertension, priapism, and leg ulcers and may be relatively protected from vaso-occlusive pain.

Fabry disease is the most common of the lysosomal storage disorders and results from deficient activity of the enzyme alpha-galactosidase A (a-Gal A), leading to progressive lysosomal deposition of globotriaosylceramide and its derivatives in cells throughout the body. The classic form, occurring in males with less than 1% a-Gal A enzyme activity, usually has its onset in childhood or adolescence with periodic crises of severe pain in the extremities (acroparesthesia), the appearance of vascular cutaneous lesions (angiokeratomas), sweating abnormalities (anhidrosis, hypohidrosis, and rarely hyperhidrosis), characteristic corneal and lenticular opacities, and proteinuria. Gradual deterioration of renal function to end-stage renal disease (ESRD) usually occurs in men in the third to fifth decade. In middle age, most males successfully treated for ESRD develop cardiac and/or cerebrovascular disease, a major cause of morbidity and mortality. Heterozygous females typically have milder symptoms at a later age of onset than males. Rarely, females may be relatively asymptomatic throughout a normal life span or may have symptoms as severe as those observed in males with the classic phenotype. In contrast, late-onset forms occur in males with greater than 1% a-Gal A activity. Clinical manifestations include cardiac disease, which usually presents in the sixth to eighth decade with left ventricular hypertrophy, cardiomyopathy, arrhythmia, and proteinuria; renal failure, associated with ESRD but without the skin lesions or pain; or cerebrovascular disease presenting as stroke or transient ischemic attack.

Familial dysautonomia, which affects the development and survival of sensory, sympathetic, and parasympathetic neurons, is a debilitating disorder present from birth. Neuronal degeneration progresses throughout life. Affected individuals have gastrointestinal dysfunction, autonomic crises (i.e., hypertensive vomiting attacks), recurrent pneumonia, altered pain sensitivity, altered temperature perception, and blood pressure instability. Hypotonia contributes to delay in acquisition of motor milestones. Optic neuropathy results in progressive vision loss. Older individuals often have a broad-based and ataxic gait that deteriorates over time. Developmental delay / intellectual disability occur in about 21% of individuals. Life expectancy is decreased.

Hallermann-Streiff syndrome is characterized by a typical skull shape (brachycephaly with frontal bossing), hypotrichosis, microphthalmia, cataracts, beaked nose, micrognathia, skin atrophy, dental anomalies, and proportionate short stature (Hallermann, 1948; Streiff, 1950; Francois, 1958). Mental retardation is present in a minority of cases (Gorlin et al., 1990).

Von Hippel-Lindau (VHL) syndrome is characterized by hemangioblastomas of the brain, spinal cord, and retina; renal cysts and clear cell renal cell carcinoma; pheochromocytoma, pancreatic cysts, and neuroendocrine tumors; endolymphatic sac tumors; and epididymal and broad ligament cysts. Cerebellar hemangioblastomas may be associated with headache, vomiting, gait disturbances, or ataxia. Spinal hemangioblastomas and related syrinx usually present with pain. Sensory and motor loss may develop with cord compression. Retinal hemangioblastomas may be the initial manifestation of VHL syndrome and can cause vision loss. Renal cell carcinoma occurs in about 70% of individuals with VHL and is the leading cause of mortality. Pheochromocytomas can be asymptomatic but may cause sustained or episodic hypertension. Pancreatic lesions often remain asymptomatic and rarely cause endocrine or exocrine insufficiency. Endolymphatic sac tumors can cause hearing loss of varying severity, which can be a presenting symptom. Cystadenomas of the epididymis are relatively common. They rarely cause problems, unless bilateral, in which case they may result in infertility.

Multiple endocrine neoplasia type 2 (MEN2) includes the following phenotypes: MEN2A, FMTC (familial medullary thyroid carcinoma, which may be a variant of MEN2A), and MEN2B. All three phenotypes involve high risk for development of medullary carcinoma of the thyroid (MTC); MEN2A and MEN2B involve an increased risk for pheochromocytoma; MEN2A involves an increased risk for parathyroid adenoma or hyperplasia. Additional features in MEN2B include mucosal neuromas of the lips and tongue, distinctive facies with enlarged lips, ganglioneuromatosis of the gastrointestinal tract, and a marfanoid habitus. MTC typically occurs in early childhood in MEN2B, early adulthood in MEN2A, and middle age in FMTC.

Neurofibromatosis 1 (NF1) is a multisystem disorder characterized by multiple café au lait macules, intertriginous freckling, multiple cutaneous neurofibromas, and learning disability or behavior problems. About half of people with NF1 have plexiform neurofibromas, but most are internal and not suspected clinically. Plexiform neurofibromas can cause pain, neurologic deficits, and abnormalities of involved or adjacent structures. Less common but potentially more serious manifestations include optic nerve and other central nervous system gliomas, malignant peripheral nerve sheath tumors, scoliosis, tibial dysplasia, vasculopathy, and gastrointestinal, endocrine, or pulmonary disease.

Idiopathic intracranial hypertension is a neurological disorder characterized by isolated increased intracranial pressure manifesting with recurrent and persistent headaches, nausea, vomiting, progressive and transient obstruction of the visual field, papilledema. Visual loss can be irreversible.

The stiff-person syndrome (SPS) is most often an adult-onset sporadic acquired disorder characterized by progressive muscle stiffness with superimposed painful muscle spasms accompanied by electromyographic evidence of continuous motor activity at rest. SPS has been associated with autoimmune disorders, diabetes mellitus, thyrotoxicosis, and hypopituitarism with adrenal insufficiency (George et al., 1984). Approximately 60% of patients with SPS have antibodies to glutamic acid decarboxylase (GAD2, or GAD65; 138275), the rate-limiting enzyme in the synthesis of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA), suggesting an immune-mediated pathogenesis (Folli et al., 1993). Approximately 10% of patients develop SPS as a paraneoplastic neurologic disorder associated with antibodies to amphiphysin (AMPH; 600418), an intracellular protein associated with neuronal synaptic vesicle endocytosis (Burns, 2005). See also congenital stiff-man syndrome, or hereditary hyperexplexia (149400), which is caused by mutations in subunits of the glycine receptor gene (GLRA1, 138491; GLRB, 138492). Meinck and Thompson (2002) provided a detailed review of stiff-person syndrome. They also discussed 2 possibly related conditions, progressive encephalomyelitis with rigidity (PERM), a more severe disorder with other neurologic features, and stiff-limb or stiff-leg syndrome, a focal disorder.

Hereditary coproporphyria (HCP) is an acute (hepatic) porphyria in which the acute symptoms are neurovisceral and occur in discrete episodes. Attacks typically start in the abdomen with low-grade pain that slowly increases over a period of days (not hours) with nausea progressing to vomiting. In some individuals, the pain is predominantly in the back or extremities. When an acute attack is untreated, a motor neuropathy may develop over a period of days or a few weeks. The neuropathy first appears as weakness proximally in the arms and legs, then progresses distally to involve the hands and feet. Some individuals experience respiratory insufficiency due to loss of innervation of the diaphragm and muscles of respiration. Acute attacks are associated commonly with use of certain medications, caloric deprivation, and changes in female reproductive hormones. About 20% of those with an acute attack also experience photosensitivity associated with bullae and skin fragility.

Acute intermittent porphyria (AIP), an autosomal dominant disorder, occurs in heterozygotes for an HMBS pathogenic variant that causes reduced activity of the enzyme porphobilinogen deaminase. AIP is considered "overt" in a heterozygote who was previously or is currently symptomatic; AIP is considered "latent" in a heterozygote who has never had symptoms, and typically has been identified during molecular genetic testing of at-risk family members. Note that GeneReviews does not use the term "carrier" for an individual who is heterozygous for an autosomal dominant pathogenic variant; GeneReviews reserves the term "carrier" for an individual who is heterozygous for an autosomal recessive disorder and thus is not expected to ever develop manifestations of the disorder. Overt AIP is characterized clinically by life-threatening acute neurovisceral attacks of severe abdominal pain without peritoneal signs, often accompanied by nausea, vomiting, tachycardia, and hypertension. Attacks may be complicated by neurologic findings (mental changes, convulsions, and peripheral neuropathy that may progress to respiratory paralysis), and hyponatremia. Acute attacks, which may be provoked by certain drugs, alcoholic beverages, endocrine factors, calorie restriction, stress, and infections, usually resolve within two weeks. Most individuals with AIP have one or a few attacks; about 3%-8% (mainly women) have recurrent attacks (defined as >3 attacks/year) that may persist for years. Other long-term complications are chronic renal failure, hepatocellular carcinoma (HCC), and hypertension. Attacks, which are very rare before puberty, are more common in women than men. Latent AIP. While all individuals heterozygous for an HMBS pathogenic variant that predisposes to AIP are at risk of developing overt AIP, most have latent AIP and never have symptoms.

MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes) is a multisystem disorder with protean manifestations. The vast majority of affected individuals develop signs and symptoms of MELAS between ages two and 40 years. Common clinical manifestations include stroke-like episodes, encephalopathy with seizures and/or dementia, muscle weakness and exercise intolerance, normal early psychomotor development, recurrent headaches, recurrent vomiting, hearing impairment, peripheral neuropathy, learning disability, and short stature. During the stroke-like episodes neuroimaging shows increased T2-weighted signal areas that do not correspond to the classic vascular distribution (hence the term "stroke-like"). Lactic acidemia is very common and muscle biopsies typically show ragged red fibers.

Smith-Lemli-Opitz syndrome (SLOS) is a congenital multiple-anomaly / cognitive impairment syndrome caused by an abnormality in cholesterol metabolism resulting from deficiency of the enzyme 7-dehydrocholesterol (7-DHC) reductase. It is characterized by prenatal and postnatal growth restriction, microcephaly, moderate-to-severe intellectual disability, and multiple major and minor malformations. The malformations include distinctive facial features, cleft palate, cardiac defects, underdeveloped external genitalia in males, postaxial polydactyly, and 2-3 syndactyly of the toes. The clinical spectrum is wide; individuals with normal development and only minor malformations have been described.

Williams syndrome (WS) is characterized by cardiovascular disease (elastin arteriopathy, peripheral pulmonary stenosis, supravalvar aortic stenosis, hypertension), distinctive facies, connective tissue abnormalities, intellectual disability (usually mild), a specific cognitive profile, unique personality characteristics, growth abnormalities, and endocrine abnormalities (hypercalcemia, hypercalciuria, hypothyroidism, and early puberty). Feeding difficulties often lead to poor weight gain in infancy. Hypotonia and hyperextensible joints can result in delayed attainment of motor milestones.

Liddle syndrome is an inherited form of high blood pressure (hypertension). This condition is characterized by severe hypertension that begins unusually early in life, often in childhood, although some affected individuals are not diagnosed until adulthood. Some people with Liddle syndrome have no additional signs or symptoms, especially in childhood. Over time, however, untreated hypertension can lead to heart disease or stroke, which may be fatal.\n\nIn addition to hypertension, affected individuals can have low levels of potassium in the blood (hypokalemia). Signs and symptoms of hypokalemia include muscle weakness or pain, fatigue, constipation, or heart palpitations. The shortage of potassium can also raise the pH of the blood, a condition known as metabolic alkalosis.

Adrenocorticotropic hormone (ACTH) hypersecretion by corticotroph adenomas of the pituitary result in excess cortisol secretion, or Cushing disease. The clinical features of Cushing disease include central obesity, moon facies, 'buffalo hump,' diabetes, hypertension, fatigue, easy bruising, depression, and reproductive disorders. Cushing disease is associated with increased morbidity and mortality, mainly due to cardiovascular or cerebrovascular disease and infections (summary by Perez-Rivas et al., 2015). Mutations in the USP8 gene, leading to an upregulated epidermal growth factor receptor (EGFR; 131550) pathway, have been identified in about 36 to 62% of corticotroph adenomas (summary by Mete and Lopes, 2017).

The Marshall-Smith syndrome (MRSHSS) is a malformation syndrome characterized by accelerated skeletal maturation, relative failure to thrive, respiratory difficulties, mental retardation, and unusual facies, including prominent forehead, shallow orbits, blue sclerae, depressed nasal bridge, and micrognathia (Adam et al., 2005).

Glycogen storage disease type I (GSDI) is characterized by accumulation of glycogen and fat in the liver and kidneys resulting in hepatomegaly and nephromegaly. Severely affected infants present in the neonatal period with severe hypoglycemia due to fasting intolerance. More commonly, untreated infants present at age three to four months with hepatomegaly, severe hypoglycemia with or without seizures, lactic acidosis, hyperuricemia, and hypertriglyceridemia. Affected children typically have doll-like faces with full cheeks, relatively thin extremities, short stature, and a protuberant abdomen. Xanthoma and diarrhea may be present. Impaired platelet function and development of reduced or dysfunctional von Willebrand factor can lead to a bleeding tendency with frequent epistaxis and menorrhagia in females. Individuals with untreated GSDIb are more likely to develop impaired neutrophil and monocyte function as well as chronic neutropenia resulting in recurrent bacterial infections, gingivitis, periodontitis, and genital and intestinal ulcers. Long-term complications of untreated GSDI include short stature, osteoporosis, delayed puberty, renal disease (including proximal and distal renal tubular acidosis, renal stones, and renal failure), gout, systemic hypertension, pulmonary hypertension, hepatic adenomas with potential for malignancy, pancreatitis, and polycystic ovaries. Seizures and cognitive impairment may occur in individuals with prolonged periods of hypoglycemia. Normal growth and puberty are expected in treated children. Most affected individuals live into adulthood.

17 alpha(a)-hydroxylase/17,20-lyase deficiency is a condition that affects the function of certain hormone-producing glands called the gonads (ovaries in females and testes in males) and the adrenal glands. The gonads direct sexual development before birth and during puberty and are important for reproduction. The adrenal glands, which are located on top of the kidneys, regulate the production of certain hormones, including those that control salt levels in the body. People with 17a-hydroxylase/17,20-lyase deficiency have an imbalance of many of the hormones that are made in these glands. 17a-hydroxylase/17,20-lyase deficiency is one of a group of disorders, known as congenital adrenal hyperplasias, that impair hormone production and disrupt sexual development and maturation.\n\nHormone imbalances lead to the characteristic signs and symptoms of 17a-hydroxylase/17,20-lyase deficiency, which include high blood pressure (hypertension), low levels of potassium in the blood (hypokalemia), and abnormal sexual development. The severity of the features varies. Two forms of the condition are recognized: complete 17a-hydroxylase/17,20-lyase deficiency, which is more severe, and partial 17a-hydroxylase/17,20-lyase deficiency, which is typically less so.\n\nMales and females are affected by disruptions to sexual development differently. Females (who have two X chromosomes) with 17a-hydroxylase/17,20-lyase deficiency are born with normal external female genitalia; however, the internal reproductive organs, including the uterus and ovaries, may be underdeveloped. Women with complete 17a-hydroxylase/17,20-lyase deficiency do not develop secondary sex characteristics, such as breasts and pubic hair, and do not menstruate (amenorrhea). Women with partial 17a-hydroxylase/17,20-lyase deficiency may develop some secondary sex characteristics; menstruation is typically irregular or absent. Either form of the disorder results in an inability to conceive a baby (infertility).\n\nIn affected individuals who are chromosomally male (having an X and a Y chromosome), problems with sexual development lead to abnormalities of the external genitalia. The most severely affected are born with characteristically female external genitalia and are generally raised as females. However, because they do not have female internal reproductive organs, these individuals have amenorrhea and do not develop female secondary sex characteristics. These individuals have testes, but they are abnormally located in the abdomen (undescended). Sometimes, complete 17a-hydroxylase/17,20-lyase deficiency leads to external genitalia that do not look clearly male or clearly female. Males with partial 17a-hydroxylase/17,20-lyase deficiency may have a small penis (micropenis), the opening of the urethra on the underside of the penis (hypospadias), or a scrotum divided into two lobes (bifid scrotum). Males with either complete or partial 17a-hydroxylase/17,20-lyase deficiency are also infertile.

Congenital adrenal hyperplasia due to 11-beta-hydroxylase deficiency is an autosomal recessive disorder of corticosteroid biosynthesis resulting in androgen excess, virilization, and hypertension. The defect causes decreased synthesis of cortisol and corticosterone in the zona fasciculata of the adrenal gland, resulting in accumulation of the precursors 11-deoxycortisol and 11-deoxycorticosterone; the latter is a potent salt-retaining mineralocorticoid that leads to arterial hypertension (White et al., 1991). CAH due to 11-beta-hydroxylase deficiency accounts for approximately 5 to 8% of all CAH cases; approximately 90% of cases are caused by 21-hydroxylase deficiency (201910) (White et al., 1991).

Systemic amyloidosis is a rare protein misfolding and deposition disorder caused by extracellular deposition of amyloid and leading to progressive organ failure. Amyloid is composed of highly organized proteinaceous, insoluble, and degradation-resistant fibrils. Hereditary systemic amyloidosis-2 (AMYLD2), resulting from mutation in the FGA gene, is the most common form of hereditary renal amyloidosis. The kidneys are the major affected organ, presenting with proteinuria. Other less frequently involved organs include liver, heart, autonomic nerve, and, rarely, peripheral nerve. A strong family history of coronary or vascular disease is also frequently seen (summary by Muchtar et al., 2021). The various forms of hereditary systemic amyloidosis that do not have peripheral neuropathy as part of the clinical syndrome have been referred to as 'Ostertag type' in reference to a German family described by Benno Ostertag (1932) in which several members died with renal amyloidosis. Since the form of hereditary amyloidosis caused by mutation in the FGA gene is the most common in Europe and has a clinical presentation with hypertension and proteinuria, Benson (2005) considered it a very good candidate for being the original amyloidosis described by Ostertag. For a discussion of genetic heterogeneity of hereditary systemic amyloidosis, see AMYLD1 (105210).

Alström syndrome is characterized by cone-rod dystrophy, obesity, progressive bilateral sensorineural hearing impairment, acute infantile-onset cardiomyopathy and/or adolescent- or adult-onset restrictive cardiomyopathy, insulin resistance / type 2 diabetes mellitus (T2DM), nonalcoholic fatty liver disease (NAFLD), and chronic progressive kidney disease. Cone-rod dystrophy presents as progressive visual impairment, photophobia, and nystagmus usually starting between birth and age 15 months. Many individuals lose all perception of light by the end of the second decade, but a minority retain the ability to read large print into the third decade. Children usually have normal birth weight but develop truncal obesity during their first year. Sensorineural hearing loss presents in the first decade in as many as 70% of individuals and may progress to the severe or moderately severe range (40-70 db) by the end of the first to second decade. Insulin resistance is typically accompanied by the skin changes of acanthosis nigricans, and proceeds to T2DM in the majority by the third decade. Nearly all demonstrate hypertriglyceridemia. Other findings can include endocrine abnormalities (hypothyroidism, hypogonadotropic hypogonadism in males, and hyperandrogenism in females), urologic dysfunction / detrusor instability, progressive decrease in renal function, and hepatic disease (ranging from elevated transaminases to steatohepatitis/NAFLD). Approximately 20% of affected individuals have delay in early developmental milestones, most commonly in gross and fine motor skills. About 30% have a learning disability. Cognitive impairment (IQ <70) is very rare. Wide clinical variability is observed among affected individuals, even within the same family.

Familial hypomagnesemia with hypercalciuria and nephrocalcinosis is a progressive renal disorder characterized by excessive urinary Ca(2+) and Mg(2+) excretion. There is progressive loss of kidney function, and in about 50% of cases, the need for renal replacement therapy arises as early as the second decade of life (summary by Muller et al., 2006). Amelogenesis imperfecta may also be present in some patients (Bardet et al., 2016). A similar disorder with renal magnesium wasting, renal failure, and nephrocalcinosis (HOMG5; 248190) is caused by mutations in another tight-junction gene, CLDN19 (610036), and is distinguished by the association of severe ocular involvement. For a discussion of phenotypic and genetic heterogeneity of familial hypomagnesemia, see HOMG1 (602014).

Sneddon syndrome is a noninflammatory arteriopathy characterized by onset of livedo reticularis in the second decade and onset of cerebrovascular disease in early adulthood (summary by Bras et al., 2014). Livedo reticularis occurs also with polyarteritis nodosa, systemic lupus erythematosus, and central thrombocythemia, any one of which may be accompanied by cerebrovascular accidents (Bruyn et al., 1987).

Apparent mineralocorticoid excess (AME) is an autosomal recessive form of low-renin hypertension associated with low aldosterone, metabolic alkalosis, hypernatremia, and hypokalemia. The disorder is due to a congenital defect in 11-beta-hydroxysteroid dehydrogenase type II (HSD11B2) activity, resulting in decreased conversion of biologically active cortisol to inactive cortisone; this defect allows cortisol to act as a ligand for the mineralocorticoid receptor, resulting in sodium retention and volume expansion. There is a favorable therapeutic response to spironolactone (review by Ferrari, 2010).

Primary trimethylaminuria is characterized by a fishy odor resembling that of rotten or decaying fish that results from excess excretion of trimethylamine in the urine, breath, sweat, and reproductive fluids. No physical symptoms are associated with trimethylaminuria. Affected individuals appear normal and healthy; however, the unpleasant odor often results in social and psychological problems. Symptoms are usually present from birth and may worsen during puberty. In females, symptoms are more severe just before and during menstruation, after taking oral contraceptives, and around the time of menopause.

Glycogenosis due to glucose-6-phosphatase deficiency (G6P) type b, or glycogen storage disease (GSD) type 1b, is a type of glycogenosis due to G6P deficiency (see this term).

Glutaric aciduria III is characterized by an isolated accumulation of glutaric acid. It appears to be a 'non-disease' as it is found in healthy individuals and is associated with inconsistent symptoms in others (summary by Marlaire et al., 2014).

Isolated and classic cutis marmorata telangiectatica congenita (CMTC) are characterized by congenital skin changes including erythematous-to-violaceous, reticulated, net-like or marbled-appearing patches of skin that do not mostly or completely resolve with warming or any other acute intervention. Individuals with isolated CMTC have no other syndromic features, and skin lesions tend to fade or resolve. Those with classic CMTC may have accompanying hemihypoplasia with body asymmetry, skin atrophy or ulceration, other vascular malformations, and occasional ocular issues (early-onset glaucoma and/or peripheral retinal vascular attenuation) but do not have other malformations, dysmorphic features, or cognitive impairment. The most common location for the CMTC lesions is on the legs. An affected limb may also display weakness or be unusually susceptible to cold compared to an unaffected limb. In more than half of affected individuals, skin lesions will generally fade across a wide range in age (6 weeks to 26 years), most commonly in the first year of life, but may not resolve completely.

A rare, genetic hypertension characterized by an adult onset of increased blood pressure associated with nephropathy progressing to end-stage renal disease. Renal biopsy may show interstitial fibrosis, glomerulosclerosis and mild tubular atrophy. Increased serum creatinine and proteinuria have also been reported.

Glomerulopathy with fibronectin deposits (GFND) is a genetically heterogeneous autosomal dominant disorder characterized clinically by proteinuria, microscopic hematuria, and hypertension that leads to end-stage renal failure in the second to fifth decade of life. Pathologic examination shows enlarged glomeruli with mesangial and subendothelial fibrillary deposits that show strong immunoreactivity to fibronectin (FN1; 135600) (Castelletti et al., 2008). Genetic Heterogeneity of Glomerulopathy with Fibronectin Deposits The GFND1 locus maps to chromosome 1q32. See also GFND2 (601894), which is caused by mutation in the FN1 gene (135600) on chromosome 2q35.

Cockayne syndrome (referred to as CS in this GeneReview) spans a continuous phenotypic spectrum that includes: CS type I, the "classic" or "moderate" form; CS type II, a more severe form with symptoms present at birth; this form overlaps with cerebrooculofacioskeletal (COFS) syndrome; CS type III, a milder and later-onset form; COFS syndrome, a fetal form of CS. CS type I is characterized by normal prenatal growth with the onset of growth and developmental abnormalities in the first two years. By the time the disease has become fully manifest, height, weight, and head circumference are far below the fifth percentile. Progressive impairment of vision, hearing, and central and peripheral nervous system function leads to severe disability; death typically occurs in the first or second decade. CS type II is characterized by growth failure at birth, with little or no postnatal neurologic development. Congenital cataracts or other structural anomalies of the eye may be present. Affected children have early postnatal contractures of the spine (kyphosis, scoliosis) and joints. Death usually occurs by age five years. CS type III is a phenotype in which major clinical features associated with CS only become apparent after age two years; growth and/or cognition exceeds the expectations for CS type I. COFS syndrome is characterized by very severe prenatal developmental anomalies (arthrogryposis and microphthalmia).

Cockayne syndrome (referred to as CS in this GeneReview) spans a continuous phenotypic spectrum that includes: CS type I, the "classic" or "moderate" form; CS type II, a more severe form with symptoms present at birth; this form overlaps with cerebrooculofacioskeletal (COFS) syndrome; CS type III, a milder and later-onset form; COFS syndrome, a fetal form of CS. CS type I is characterized by normal prenatal growth with the onset of growth and developmental abnormalities in the first two years. By the time the disease has become fully manifest, height, weight, and head circumference are far below the fifth percentile. Progressive impairment of vision, hearing, and central and peripheral nervous system function leads to severe disability; death typically occurs in the first or second decade. CS type II is characterized by growth failure at birth, with little or no postnatal neurologic development. Congenital cataracts or other structural anomalies of the eye may be present. Affected children have early postnatal contractures of the spine (kyphosis, scoliosis) and joints. Death usually occurs by age five years. CS type III is a phenotype in which major clinical features associated with CS only become apparent after age two years; growth and/or cognition exceeds the expectations for CS type I. COFS syndrome is characterized by very severe prenatal developmental anomalies (arthrogryposis and microphthalmia).

MED12-related disorders include the phenotypes of FG syndrome type 1 (FGS1), Lujan syndrome (LS), X-linked Ohdo syndrome (XLOS), Hardikar syndrome (HS), and nonspecific intellectual disability (NSID). FGS1 and LS share the clinical findings of cognitive impairment, hypotonia, and abnormalities of the corpus callosum. FGS1 is further characterized by absolute or relative macrocephaly, tall forehead, downslanted palpebral fissures, small and simple ears, constipation and/or anal anomalies, broad thumbs and halluces, and characteristic behavior. LS is further characterized by large head, tall thin body habitus, long thin face, prominent nasal bridge, high narrow palate, and short philtrum. Carrier females in families with FGS1 and LS are typically unaffected. XLOS is characterized by intellectual disability, blepharophimosis, and facial coarsening. HS has been described in females with cleft lip and/or cleft palate, biliary and liver anomalies, intestinal malrotation, pigmentary retinopathy, and coarctation of the aorta. Developmental and cognitive concerns have not been reported in females with HS. Pathogenic variants in MED12 have been reported in an increasing number of males and females with NSID, with affected individuals often having clinical features identified in other MED12-related disorders.

Myhre syndrome is a connective tissue disorder with multisystem involvement, progressive and proliferative fibrosis that may occur spontaneously or following trauma or surgery, mild-to-moderate intellectual disability, and in some instances, autistic-like behaviors. Organ systems primarily involved include: cardiovascular (congenital heart defects, long- and short-segment stenosis of the aorta and peripheral arteries, pericardial effusion, constrictive pericarditis, restrictive cardiomyopathy, and hypertension); respiratory (choanal stenosis, laryngotracheal narrowing, obstructive airway disease, or restrictive pulmonary disease), gastrointestinal (pyloric stenosis, duodenal strictures, severe constipation); and skin (thickened particularly on the hands and extensor surfaces). Additional findings include distinctive craniofacial features and skeletal involvement (intrauterine growth restriction, short stature, limited joint range of motion). To date, 55 individuals with molecularly confirmed Myhre syndrome have been reported.

Schimke immunoosseous dysplasia (SIOD) is characterized by spondyloepiphyseal dysplasia (SED) resulting in short stature, nephropathy, and T-cell deficiency. Radiographic manifestations of SED include ovoid and mildly flattened vertebral bodies, small ilia with shallow dysplastic acetabular fossae, and small deformed capital femoral epiphyses. Nearly all affected individuals have progressive steroid-resistant nephropathy, usually developing within five years of the diagnosis of growth failure and terminating with end-stage renal disease. The majority of tested individuals have T-cell deficiency and an associated risk for opportunistic infection, a common cause of death. SIOD involves a spectrum that ranges from an infantile or severe early-onset form with a greater risk of death during childhood to a juvenile or milder later-onset form with likely survival into adulthood if renal disease is appropriately treated.

WT1 disorder is characterized by congenital/infantile or childhood onset of steroid-resistant nephrotic syndrome (SRNS), a progressive glomerulopathy that does not respond to standard steroid therapy. Additional common findings can include disorders of testicular development (with or without abnormalities of the external genitalia and/or müllerian structures) and Wilms tumor. Less common findings are congenital anomalies of the kidney and urinary tract (CAKUT) and gonadoblastoma. While various combinations of renal and other findings associated with a WT1 pathogenic variant were designated as certain syndromes in the past, those designations are now recognized to be part of a phenotypic continuum and are no longer clinically helpful.

Pseudoxanthoma elasticum (PXE) is a systemic disorder that affects the elastic tissue of the skin, the eye, and vascular system. Individuals most commonly present with angioid streaks of the retina found on routine eye examination or associated with retinal hemorrhage and/or characteristic papules in the skin. The most frequent cause of morbidity and disability in PXE is reduced vision due to complications of subretinal neovascularizations and macular atrophy. Other manifestations include premature gastrointestinal angina and/or bleeding, intermittent claudication of arm and leg muscles, stroke, renovascular hypertension, and cardiovascular complications (angina/myocardial infarction). Most affected individuals live a normal life span.

Oral-facial-digital syndrome type I (OFD1) is usually male lethal during gestation and predominantly affects females. OFD1 is characterized by the following features: Oral (lobulated tongue, tongue nodules, cleft of the hard or soft palate, accessory gingival frenulae, hypodontia, and other dental abnormalities). Facial (widely spaced eyes or telecanthus, hypoplasia of the alae nasi, median cleft or pseudocleft upper lip, micrognathia). Digital (brachydactyly, syndactyly, clinodactyly of the fifth finger; duplicated hallux [great toe]). Kidney (polycystic kidney disease). Brain (e.g., intracerebral cysts, agenesis of the corpus callosum, cerebellar agenesis with or without Dandy-Walker malformation). Intellectual disability (in ~50% of individuals).

Renal hypodysplasia/aplasia belongs to a group of perinatally lethal renal diseases, including bilateral renal aplasia, unilateral renal agenesis with contralateral dysplasia (URA/RD), and severe obstructive uropathy. Renal aplasia falls at the most severe end of the spectrum of congenital anomalies of the kidney and urinary tract (CAKUT; 610805), and usually results in death in utero or in the perinatal period. Families have been documented in which bilateral renal agenesis or aplasia coexists with unilateral renal aplasia, renal dysplasia, or renal aplasia with renal dysplasia, suggesting that these conditions may belong to a pathogenic continuum or phenotypic spectrum (summary by Joss et al., 2003; Humbert et al., 2014). Genetic Heterogeneity of Renal Hypodysplasia/Aplasia See also RHDA2 (615721), caused by mutation in the FGF20 gene (605558) on chromosome 8p22; RHDA3 (617805), caused by mutation in the GREB1L gene (617782) on chromosome 18q11; and RHDA4 (619887), caused by mutation in the GFRA1 gene (601496) on chromosome 10q25.

Familial partial lipodystrophy type 1 (FPLD1), or Kobberling-type lipodystrophy, is characterized by loss of adipose tissue confined to the extremities, with normal or increased distribution of fat on the face, neck, and trunk (Kobberling and Dunnigan, 1986). For a general description and a discussion of genetic heterogeneity of familial partial lipodystrophy (FPLD), see 151660.

Familial partial lipodystrophy (FPLD) is a metabolic disorder characterized by abnormal subcutaneous adipose tissue distribution beginning in late childhood or early adult life. Affected individuals gradually lose fat from the upper and lower extremities and the gluteal and truncal regions, resulting in a muscular appearance with prominent superficial veins. In some patients, adipose tissue accumulates on the face and neck, causing a double chin, fat neck, or cushingoid appearance. Metabolic abnormalities include insulin-resistant diabetes mellitus with acanthosis nigricans and hypertriglyceridemia; hirsutism and menstrual abnormalities occur infrequently. Familial partial lipodystrophy may also be referred to as lipoatrophic diabetes mellitus, but the essential feature is loss of subcutaneous fat (review by Garg, 2004). The disorder may be misdiagnosed as Cushing disease (see 219080) (Kobberling and Dunnigan, 1986; Garg, 2004). Genetic Heterogeneity of Familial Partial Lipodystrophy Familial partial lipodystrophy is a clinically and genetically heterogeneous disorder. Types 1 and 2 were originally described as clinical subtypes: type 1 (FPLD1; 608600), characterized by loss of subcutaneous fat confined to the limbs (Kobberling et al., 1975), and FPLD2, characterized by loss of subcutaneous fat from the limbs and trunk (Dunnigan et al., 1974; Kobberling and Dunnigan, 1986). No genetic basis for FPLD1 has yet been delineated. FPLD3 (604367) is caused by mutation in the PPARG gene (601487) on chromosome 3p25; FPLD4 (613877) is caused by mutation in the PLIN1 gene (170290) on chromosome 15q26; FPLD5 (615238) is caused by mutation in the CIDEC gene (612120) on chromosome 3p25; FPLD6 (615980) is caused by mutation in the LIPE gene (151750) on chromosome 19q13; FPLD7 (606721) is caused by mutation in the CAV1 gene (601047) on chromosome 7q31; FPLD8 (620679), caused by mutation in the ADRA2A gene (104210) on chromosome 10q25; and FPLD9 (620683), caused by mutation in the PLAAT3 gene (613867) on chromosome 11q12.

A rare familial partial lipodystrophy with characteristics of adult onset of distal lipoatrophy with gluteofemoral fat loss, as well as increased fat accumulation in the face and trunk and visceral adiposity. Additional manifestations include diabetes mellitus, atherogenic dyslipidemia, eyelid xanthelasma, arterial hypertension, cardiovascular disease, hepatic steatosis, acanthosis nigricans on axilla and neck, hirsutism, and muscular hypertrophy of the lower limbs. Caused by heterozygous mutation in the PPARG gene on chromosome 3p25.

Pierson syndrome (PIERS) is an autosomal recessive disorder comprising congenital nephrotic syndrome with diffuse mesangial sclerosis and distinct ocular abnormalities, including microcoria and hypoplasia of the ciliary and pupillary muscles, as well as other anomalies. Many patients die early, and those who survive tend to show neurodevelopmental delay and visual loss (summary by Zenker et al., 2004). Mutations in the LAMB2 gene also cause nephrotic syndrome type 5 with or without mild ocular anomalies (NPHS5; 614199).

Hereditary hemorrhagic telangiectasia (HHT) is characterized by the presence of multiple arteriovenous malformations (AVMs) that lack intervening capillaries and result in direct connections between arteries and veins. The most common clinical manifestation is spontaneous and recurrent nosebleeds (epistaxis) beginning on average at age 12 years. Telangiectases (small AVMs) are characteristically found on the lips, tongue, buccal and gastrointestinal (GI) mucosa, face, and fingers. The appearance of telangiectases is generally later than epistaxis but may be during childhood. Large AVMs occur most often in the lungs, liver, or brain; complications from bleeding or shunting may be sudden and catastrophic. A minority of individuals with HHT have GI bleeding, which is rarely seen before age 50 years.

Pseudohypoaldosteronism type II (PHAII) is characterized by hyperkalemia despite normal glomerular filtration rate (GFR) and frequently by hypertension. Other associated findings in both children and adults include hyperchloremia, metabolic acidosis, and suppressed plasma renin levels. Aldosterone levels are variable, but are relatively low given the degree of hyperkalemia (elevated serum potassium is a potent stimulus for aldosterone secretion). Hypercalciuria is well described.

Pseudohypoaldosteronism type II (PHAII) is characterized by hyperkalemia despite normal glomerular filtration rate (GFR) and frequently by hypertension. Other associated findings in both children and adults include hyperchloremia, metabolic acidosis, and suppressed plasma renin levels. Aldosterone levels are variable, but are relatively low given the degree of hyperkalemia (elevated serum potassium is a potent stimulus for aldosterone secretion). Hypercalciuria is well described.

Pseudohypoaldosteronism type II (PHAII) is characterized by hyperkalemia despite normal glomerular filtration rate (GFR) and frequently by hypertension. Other associated findings in both children and adults include hyperchloremia, metabolic acidosis, and suppressed plasma renin levels. Aldosterone levels are variable, but are relatively low given the degree of hyperkalemia (elevated serum potassium is a potent stimulus for aldosterone secretion). Hypercalciuria is well described.

Heme oxygenase-1 deficiency (HMOX1D) is a rare autosomal recessive disorder with a complex clinical presentation including direct antibody negative hemolytic anemia, low bilirubin, and hyperinflammation (summary by Chau et al., 2020). Other features may include asplenia and nephritis (Radhakrishnan et al., 2011).

Generalized glucocorticoid resistance is an autosomal dominant disease characterized by increased plasma cortisol concentration and high urinary free cortisol, resistance to adrenal suppression by dexamethasone, and the absence of clinical stigmata of Cushing syndrome. The clinical expression of the disease is variable. Common features include hypoglycemia, hypertension, and metabolic alkalosis. In females, overproduction of adrenal androgens has been associated with infertility, male-pattern baldness, hirsutism, and menstrual irregularities. Other features include chronic fatigue and profound anxiety (summary by Chrousos et al., 1983; Donner et al., 2013).

Coronary artery disease (CAD) and its most important complication, acute myocardial infarction (MI), are leading causes of death and disability in the developed world. Multiple risk factors for CAD/MI have been identified, including family history, hypertension, hypercholesterolemia, obesity, smoking, and diabetes. Several genomewide scans of affected sib pairs have identified susceptibility loci for CAD, e.g., 607339 and 300464.

Focal segmental glomerulosclerosis (FSGS) is a pathologic entity associated clinically with proteinuria, the nephrotic syndrome (NPHS), and progressive loss of renal function. It is a common cause of end-stage renal disease (ESRD) (Meyrier, 2005). For a general phenotypic description and a discussion of genetic heterogeneity of focal segmental glomerulosclerosis and nephrotic syndrome, see FSGS1 (603278).

Short-rib thoracic dysplasia (SRTD) with or without polydactyly refers to a group of autosomal recessive skeletal ciliopathies that are characterized by a constricted thoracic cage, short ribs, shortened tubular bones, and a 'trident' appearance of the acetabular roof. SRTD encompasses Ellis-van Creveld syndrome (EVC) and the disorders previously designated as Jeune syndrome or asphyxiating thoracic dystrophy (ATD), short rib-polydactyly syndrome (SRPS), and Mainzer-Saldino syndrome (MZSDS). Polydactyly is variably present, and there is phenotypic overlap in the various forms of SRTDs, which differ by visceral malformation and metaphyseal appearance. Nonskeletal involvement can include cleft lip/palate as well as anomalies of major organs such as the brain, eye, heart, kidneys, liver, pancreas, intestines, and genitalia. Some forms of SRTD are lethal in the neonatal period due to respiratory insufficiency secondary to a severely restricted thoracic cage, whereas others are compatible with life (summary by Huber and Cormier-Daire, 2012 and Schmidts et al., 2013). There is phenotypic overlap with the cranioectodermal dysplasias (Sensenbrenner syndrome; see CED1, 218330). For a discussion of genetic heterogeneity of short-rib thoracic dysplasia, see SRTD1 (208500).

Beare-Stevenson cutis gyrata syndrome (BSTVS) is an autosomal dominant condition characterized by the furrowed skin disorder of cutis gyrata, acanthosis nigricans, craniosynostosis, craniofacial dysmorphism, digital anomalies, umbilical and anogenital abnormalities, and early death (summary by Przylepa et al., 1996).

A rare immune complex-mediated vasculitis characterized by the presence of circulating cryoprecipitable immune complexes in the serum, manifesting clinically with the classical triad of purpura, weakness and arthralgia.

Corticosteroid-binding globulin deficiency is a condition with subtle signs and symptoms, the most frequent being extreme tiredness (fatigue), especially after physical exertion. Many people with this condition have unusually low blood pressure (hypotension). Some affected individuals have a fatty liver or experience chronic pain, particularly in their muscles. These features vary among affected individuals, even those within the same family.\n\nMany people with corticosteroid-binding globulin deficiency have only one or two of these features; others have no signs and symptoms of the disorder and are only diagnosed after a relative is found to be affected.\n\nSome people with corticosteroid-binding globulin deficiency also have a condition called myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). The features of ME/CFS are prolonged fatigue that interferes with daily activities, as well as general symptoms, such as sore throat or headaches.

PAX2-related disorder is an autosomal dominant disorder associated with renal and eye abnormalities. The disorder was originally referred to as renal coloboma syndrome and characterized by renal hypodysplasia and abnormalities of the optic nerve; with improved access to molecular testing, a wider range of phenotypes has been recognized in association with pathogenic variants in PAX2. Abnormal renal structure or function is noted in 92% of affected individuals and ophthalmologic abnormalities in 77% of affected individuals. Renal abnormalities can be clinically silent in rare individuals. In most individuals, clinically significant renal insufficiency / renal failure is reported. End-stage renal disease requiring renal transplant is not uncommon. Uric acid nephrolithiasis has been reported. Ophthalmologic abnormalities are typically described as optic nerve coloboma or dysplasia. Iris colobomas have not been reported in any individual with PAX2–related disorder. Ophthalmologic abnormalities may significantly impair vision in some individuals, while others have subtle changes only noted after detailed ophthalmologic examination. Additional clinical findings include high-frequency sensorineural hearing loss, soft skin, and ligamentous laxity. PAX2 pathogenic variants have been identified in multiple sporadic and familial cases of nonsyndromic renal disease including renal hypodysplasia and focal segmental glomerulosclerosis.

Familial hyperaldosteronism type II (HALD2) is an autosomal dominant disorder characterized by hypertension due to increased aldosterone, often with hypokalemia. Patients usually present before age 20 years, although some may present in infancy. The disorder shows incomplete penetrance and variable expressivity; some patients may have normal blood pressure but have an increased aldosterone:renin ratio (ARR) on laboratory testing. Spironolactone is an effective treatment (summary by Scholl et al., 2018). For a general phenotypic description and a discussion of genetic heterogeneity of familial hyperaldosteronism, see HALD1 (103900).

Hypertension due to gain-of-function mutations in the mineralocorticoid receptor is a rare genetic hypertension characterized by a familial severe hypertension with an onset before age 20 years, associated with suppressed plasma renin and low aldosterone levels in the presence of low or normal levels of the mineralocorticoid aldosterone, that is highly resistant to antihypertensive medication. During pregnancy, there is a marked exacerbation of hypertension, accompanied by low serum potassium levels and undetectable aldosterone levels, but without signs of preeclampsia, requiring early delivery.

Keutel syndrome (KTLS) is an autosomal recessive disorder characterized by multiple peripheral pulmonary stenoses, brachytelephalangy, inner ear deafness, and abnormal cartilage ossification or calcification (summary by Khosroshahi et al., 2014).

Classic Joubert syndrome (JS) is characterized by three primary findings: A distinctive cerebellar and brain stem malformation called the molar tooth sign (MTS). Hypotonia. Developmental delays. Often these findings are accompanied by episodic tachypnea or apnea and/or atypical eye movements. In general, the breathing abnormalities improve with age, truncal ataxia develops over time, and acquisition of gross motor milestones is delayed. Cognitive abilities are variable, ranging from severe intellectual disability to normal. Additional findings can include retinal dystrophy, renal disease, ocular colobomas, occipital encephalocele, hepatic fibrosis, polydactyly, oral hamartomas, and endocrine abnormalities. Both intra- and interfamilial variation are seen.

The nephronophthisis (NPH) phenotype is characterized by reduced renal concentrating ability, chronic tubulointerstitial nephritis, cystic renal disease, and progression to end-stage renal disease (ESRD) before age 30 years. Three age-based clinical subtypes are recognized: infantile, juvenile, and adolescent/adult. Infantile NPH can present in utero with oligohydramnios sequence (limb contractures, pulmonary hypoplasia, and facial dysmorphisms) or postnatally with renal manifestations that progress to ESRD before age 3 years. Juvenile NPH, the most prevalent subtype, typically presents with polydipsia and polyuria, growth retardation, chronic iron-resistant anemia, or other findings related to chronic kidney disease (CKD). Hypertension is typically absent due to salt wasting. ESRD develops at a median age of 13 years. Ultrasound findings are increased echogenicity, reduced corticomedullary differentiation, and renal cysts (in 50% of affected individuals). Histologic findings include tubulointerstitial fibrosis, thickened and disrupted tubular basement membrane, sporadic corticomedullary cysts, and normal or reduced kidney size. Adolescent/adult NPH is clinically similar to juvenile NPH, but ESRD develops at a median age of 19 years. Within a subtype, inter- and intrafamilial variability in rate of progression to ESRD is considerable. Approximately 80%-90% of individuals with the NPH phenotype have no extrarenal features (i.e., they have isolated NPH); ~10%-20% have extrarenal manifestations that constitute a recognizable syndrome (e.g., Joubert syndrome, Bardet-Biedl syndrome, Jeune syndrome and related skeletal disorders, Meckel-Gruber syndrome, Senior-Løken syndrome, Leber congenital amaurosis, COACH syndrome, and oculomotor apraxia, Cogan type).

Mitochondrial complex IV deficiency nuclear type 5 (MC4DN5) is an autosomal recessive severe metabolic multisystemic disorder with onset in infancy. Features include delayed psychomotor development, impaired intellectual development with speech delay, mild dysmorphic facial features, hypotonia, ataxia, and seizures. There is increased serum lactate and episodic hypoglycemia. Some patients may have cardiomyopathy, abnormal breathing, or liver abnormalities, reflecting systemic involvement. Brain imaging shows lesions in the brainstem and basal ganglia, consistent with a diagnosis of Leigh syndrome (see 256000). Affected individuals tend to have episodic metabolic and/or neurologic crises in early childhood, which often lead to early death (summary by Debray et al., 2011). For a discussion of genetic heterogeneity of mitochondrial complex IV (cytochrome c oxidase) deficiency, see 220110.

ACTH-independent macronodular adrenal hyperplasia (AIMAH) is an endogenous form of adrenal Cushing syndrome characterized by multiple bilateral adrenocortical nodules that cause a striking enlargement of the adrenal glands. Although some familial cases have been reported, the vast majority of AIMAH cases are sporadic. Patients typically present in the fifth or sixth decade of life, approximately 10 years later than most patients with other causes of Cushing syndrome (Swain et al., 1998; Christopoulos et al., 2005). Approximately 10 to 15% of adrenal Cushing syndrome is due to primary bilateral ACTH-independent adrenocortical pathology. The 2 main subtypes are AIMAH and primary pigmented nodular adrenocortical disease (PPNAD; see 610489), which is often a component of the Carney complex (160980) and associated with mutations in the PRKAR1A gene (188830). AIMAH is rare, representing less than 1% of endogenous causes of Cushing syndrome (Swain et al., 1998; Christopoulos et al., 2005). See also ACTH-independent Cushing syndrome (615830) due to somatic mutation in the PRKACA gene (601639). Cushing 'disease' (219090) is an ACTH-dependent disorder caused in most cases by pituitary adenomas that secrete excessive ACTH. Genetic Heterogeneity of ACTH-Independent Macronodular Adrenal Hyperplasia AIMAH2 (615954) is caused by germline mutation on 1 allele of the ARMC5 gene (615549) coupled with a somatic mutation in the other allele. AIMAH3 (620990) is caused by germline mutation on 1 allele of the KDM1A gene (609132) coupled with a somatic mutation in the other allele.

Alagille syndrome (ALGS) is a multisystem disorder with a wide spectrum of clinical variability; this variability is seen even among individuals from the same family. The major clinical manifestations of ALGS are bile duct paucity on liver biopsy, cholestasis, congenital cardiac defects (primarily involving the pulmonary arteries), butterfly vertebrae, ophthalmologic abnormalities (most commonly posterior embryotoxon), and characteristic facial features. Renal abnormalities, growth failure, developmental delays, splenomegaly, and vascular abnormalities may also occur.

Focal segmental glomerulosclerosis (FSGS) is a pathologic entity associated clinically with proteinuria, the nephrotic syndrome (NPHS), and progressive loss of renal function. It is a common cause of end-stage renal disease (ESRD) (review by Meyrier, 2005). For a general phenotypic description and a discussion of genetic heterogeneity of focal segmental glomerulosclerosis and nephrotic syndrome (NPHS), see FSGS1 (603278).

Microcephalic osteodysplastic primordial dwarfism type I (MOPD1) is a severe autosomal recessive skeletal dysplasia characterized by dwarfism, microcephaly, and neurologic abnormalities, including mental retardation, brain malformations, and ocular/auditory sensory deficits. Patients often die in early childhood (summary by Pierce and Morse, 2012).

Arterial tortuosity syndrome (ATS) is characterized by widespread elongation and tortuosity of the aorta and mid-sized arteries as well as focal stenosis of segments of the pulmonary arteries and/or aorta combined with findings of a generalized connective tissue disorder, which may include soft or doughy hyperextensible skin, joint hypermobility, inguinal hernia, and diaphragmatic hernia. Skeletal findings include pectus excavatum or carinatum, arachnodactyly, scoliosis, knee/elbow contractures, and camptodactyly. The cardiovascular system is the major source of morbidity and mortality with increased risk at any age for aneurysm formation and dissection both at the aortic root and throughout the arterial tree, and for ischemic vascular events involving cerebrovascular circulation (resulting in non-hemorrhagic stroke) and the abdominal arteries (resulting in infarctions of abdominal organs).

Cirrhosis in which no causative agent can be identified.

The hypertension and brachydactyly syndrome (HTNB) is characterized by brachydactyly type E, severe salt-independent but age-dependent hypertension, an increased fibroblast growth rate, neurovascular contact at the rostral-ventrolateral medulla, altered baroreflex blood pressure regulation, and death from stroke before age 50 years when untreated (summary by Maass et al., 2015).

Primary pigmented nodular adrenocortical disease (PPNAD) is a form of ACTH-independent adrenal hyperplasia resulting in Cushing syndrome. It is usually seen as a manifestation of the Carney complex (CNC1; 160980), a multiple neoplasia syndrome. However, PPNAD can also occur in isolation (Groussin et al., 2002). Genetic Heterogeneity of Primary Pigmented Nodular Adrenocortical Disease See also PPNAD2 (610475), caused by mutation in the PDE11A gene (604961) on chromosome 2q31; PPNAD3 (614190), caused by mutation in the PDE8B gene (603390) on chromosome 5q13; and PPNAD4 (615830), caused by a duplication on chromosome 19p13 that includes the PRKACA gene (601639).

Any primary pigmented nodular adrenocortical disease in which the cause of the disease is a mutation in the PDE11A gene.

The nephronophthisis (NPH) phenotype is characterized by reduced renal concentrating ability, chronic tubulointerstitial nephritis, cystic renal disease, and progression to end-stage renal disease (ESRD) before age 30 years. Three age-based clinical subtypes are recognized: infantile, juvenile, and adolescent/adult. Infantile NPH can present in utero with oligohydramnios sequence (limb contractures, pulmonary hypoplasia, and facial dysmorphisms) or postnatally with renal manifestations that progress to ESRD before age 3 years. Juvenile NPH, the most prevalent subtype, typically presents with polydipsia and polyuria, growth retardation, chronic iron-resistant anemia, or other findings related to chronic kidney disease (CKD). Hypertension is typically absent due to salt wasting. ESRD develops at a median age of 13 years. Ultrasound findings are increased echogenicity, reduced corticomedullary differentiation, and renal cysts (in 50% of affected individuals). Histologic findings include tubulointerstitial fibrosis, thickened and disrupted tubular basement membrane, sporadic corticomedullary cysts, and normal or reduced kidney size. Adolescent/adult NPH is clinically similar to juvenile NPH, but ESRD develops at a median age of 19 years. Within a subtype, inter- and intrafamilial variability in rate of progression to ESRD is considerable. Approximately 80%-90% of individuals with the NPH phenotype have no extrarenal features (i.e., they have isolated NPH); ~10%-20% have extrarenal manifestations that constitute a recognizable syndrome (e.g., Joubert syndrome, Bardet-Biedl syndrome, Jeune syndrome and related skeletal disorders, Meckel-Gruber syndrome, Senior-Løken syndrome, Leber congenital amaurosis, COACH syndrome, and oculomotor apraxia, Cogan type).

Glomerulopathy with fibronectin deposits is a genetically heterogeneous autosomal dominant disorder characterized clinically by proteinuria, microscopic hematuria, and hypertension that leads to end-stage renal failure in the second to fifth decade of life. Pathologic examination shows enlarged glomeruli with mesangial and subendothelial fibrillary deposits that show strong immunoreactivity to fibronectin (Castelletti et al., 2008). For a discussion of genetic heterogeneity of GFND, see 137950.

Scalp-ear-nipple syndrome is characterized by aplasia cutis congenita of the scalp, breast anomalies that range from hypothelia or athelia to amastia, and minor anomalies of the external ears. Less frequent clinical characteristics include nail dystrophy, dental anomalies, cutaneous syndactyly of the digits, and renal malformations. Penetrance appears to be high, although there is substantial variable expressivity within families (Marneros et al., 2013).

Autosomal dominant tubulointerstitial kidney disease – MUC1 (ADTKD-MUC1) is characterized by slowly progressive tubulointerstitial disease that leads to end-stage renal disease (ESRD) and the need for dialysis or kidney transplantation. The rate of loss of kidney function for individuals is variable within and between families, with a median age of onset of end-stage renal disease (ESRD) of 46 years (range: ages 20-70 years). There are no other systemic manifestations.

Gaucher disease (GD) encompasses a continuum of clinical findings from a perinatal lethal disorder to an asymptomatic type. The identification of three major clinical types (1, 2, and 3) and two other subtypes (perinatal-lethal and cardiovascular) is useful in determining prognosis and management. GD type 1 is characterized by the presence of clinical or radiographic evidence of bone disease (osteopenia, focal lytic or sclerotic lesions, and osteonecrosis), hepatosplenomegaly, anemia and thrombocytopenia, lung disease, and the absence of primary central nervous system disease. GD types 2 and 3 are characterized by the presence of primary neurologic disease; in the past, they were distinguished by age of onset and rate of disease progression, but these distinctions are not absolute. Disease with onset before age two years, limited psychomotor development, and a rapidly progressive course with death by age two to four years is classified as GD type 2. Individuals with GD type 3 may have onset before age two years, but often have a more slowly progressive course, with survival into the third or fourth decade. The perinatal-lethal form is associated with ichthyosiform or collodion skin abnormalities or with nonimmune hydrops fetalis. The cardiovascular form is characterized by calcification of the aortic and mitral valves, mild splenomegaly, corneal opacities, and supranuclear ophthalmoplegia. Cardiopulmonary complications have been described with all the clinical subtypes, although varying in frequency and severity.

An autosomal recessive condition caused by mutation(s) in the ERCC4 gene, encoding DNA repair endonuclease XPF. it is characterized by characterized by cutaneous photosensitivity and progeroid features in multiple organ systems.

Any coronary artery disease in which the cause of the disease is a mutation in the LRP6 gene.

Multicentric carpotarsal osteolysis syndrome is a rare skeletal disorder, usually presenting in early childhood with a clinical picture mimicking juvenile rheumatoid arthritis. Progressive destruction of the carpal and tarsal bone usually occurs and other bones may also be involved. Chronic renal failure is a frequent component of the syndrome. Mental retardation and minor facial anomalies have been noted in some patients. Autosomal dominant inheritance has been documented in many families (Pai and Macpherson, 1988). See also Torg-Winchester syndrome (259600), an autosomal recessive multicentric osteolysis syndrome.

For a detailed discussion of the WAGR syndrome, see 194072. In a subgroup of individuals with the WAGR syndrome, obesity develops. The phenotype in this subset is associated with haploinsufficiency for the BDNF gene.

Syndrome with characteristics of seizures, sensorineural deafness, ataxia, intellectual deficit, and electrolyte imbalance. It has been described in five patients from four families. The disease is caused by homozygous or compound heterozygous mutations in the KCNJ10 gene, encoding a potassium channel expressed in the brain, spinal cord, inner ear and kidneys. Transmission is autosomal recessive.

Hemolytic-uremic syndrome (HUS) is characterized by hemolytic anemia, thrombocytopenia, and renal failure caused by platelet thrombi in the microcirculation of the kidney and other organs. The onset of atypical HUS (aHUS) ranges from the neonatal period to adulthood. Genetic aHUS accounts for an estimated 60% of all aHUS. Individuals with genetic aHUS frequently experience relapse even after complete recovery following the presenting episode; 60% of genetic aHUS progresses to end-stage renal disease (ESRD).

Autosomal recessive spondylometaphyseal dysplasia, Mégarbané type is a rare, primary bone dysplasia characterized by intrauterine growth retardation, pre- and postnatal disproportionate short stature with short, rhizomelic limbs, facial dysmorphism, a short neck and small thorax. Hypotonia, cardiomegaly and global developmental delay have also been associated. Several radiographic findings have been reported, including ribs with cupped ends, platyspondyly, square iliac bones, horizontal and trident acetabula, hypoplastic ischia, and delayed epiphyseal ossification.

Focal segmental glomerulosclerosis (FSGS) is a pathologic entity associated clinically with proteinuria, the nephrotic syndrome (NPHS), and progressive loss of renal function. It is a common cause of end-stage renal disease (ESRD) (Meyrier, 2005). Dominant intermediate Charcot-Marie-Tooth disease E and focal segmental glomerulonephritis (CMTDIE; 614455) is also caused by heterozygous mutation in the INF2 gene. For a general phenotypic description and a discussion of genetic heterogeneity of focal segmental glomerulosclerosis and nephrotic syndrome, see FSGS1 (603278).

Autosomal dominant polycystic kidney disease (ADPKD) is generally a late-onset multisystem disorder characterized by bilateral kidney cysts, liver cysts, and an increased risk of intracranial aneurysms. Other manifestations include: cysts in the pancreas, seminal vesicles, and arachnoid membrane; dilatation of the aortic root and dissection of the thoracic aorta; mitral valve prolapse; and abdominal wall hernias. Kidney manifestations include early-onset hypertension, kidney pain, and kidney insufficiency. Approximately 50% of individuals with ADPKD have end-stage kidney disease (ESKD) by age 60 years. The prevalence of liver cysts increases with age and occasionally results in clinically significant severe polycystic liver disease (PLD), most often in females. Overall, the prevalence of intracranial aneurysms is fivefold higher than in the general population and further increased in those with a positive family history of aneurysms or subarachnoid hemorrhage. There is substantial variability in the severity of kidney disease and other extra-kidney manifestations.

Hemolytic-uremic syndrome (HUS) is characterized by hemolytic anemia, thrombocytopenia, and renal failure caused by platelet thrombi in the microcirculation of the kidney and other organs. The onset of atypical HUS (aHUS) ranges from the neonatal period to adulthood. Genetic aHUS accounts for an estimated 60% of all aHUS. Individuals with genetic aHUS frequently experience relapse even after complete recovery following the presenting episode; 60% of genetic aHUS progresses to end-stage renal disease (ESRD).

Hemolytic-uremic syndrome (HUS) is characterized by hemolytic anemia, thrombocytopenia, and renal failure caused by platelet thrombi in the microcirculation of the kidney and other organs. The onset of atypical HUS (aHUS) ranges from the neonatal period to adulthood. Genetic aHUS accounts for an estimated 60% of all aHUS. Individuals with genetic aHUS frequently experience relapse even after complete recovery following the presenting episode; 60% of genetic aHUS progresses to end-stage renal disease (ESRD).

Hemolytic-uremic syndrome (HUS) is characterized by hemolytic anemia, thrombocytopenia, and renal failure caused by platelet thrombi in the microcirculation of the kidney and other organs. The onset of atypical HUS (aHUS) ranges from the neonatal period to adulthood. Genetic aHUS accounts for an estimated 60% of all aHUS. Individuals with genetic aHUS frequently experience relapse even after complete recovery following the presenting episode; 60% of genetic aHUS progresses to end-stage renal disease (ESRD).

Hemolytic-uremic syndrome (HUS) is characterized by hemolytic anemia, thrombocytopenia, and renal failure caused by platelet thrombi in the microcirculation of the kidney and other organs. The onset of atypical HUS (aHUS) ranges from the neonatal period to adulthood. Genetic aHUS accounts for an estimated 60% of all aHUS. Individuals with genetic aHUS frequently experience relapse even after complete recovery following the presenting episode; 60% of genetic aHUS progresses to end-stage renal disease (ESRD).

Hemolytic-uremic syndrome (HUS) is characterized by hemolytic anemia, thrombocytopenia, and renal failure caused by platelet thrombi in the microcirculation of the kidney and other organs. The onset of atypical HUS (aHUS) ranges from the neonatal period to adulthood. Genetic aHUS accounts for an estimated 60% of all aHUS. Individuals with genetic aHUS frequently experience relapse even after complete recovery following the presenting episode; 60% of genetic aHUS progresses to end-stage renal disease (ESRD).

Glycogen storage disease type I (GSDI) is characterized by accumulation of glycogen and fat in the liver and kidneys resulting in hepatomegaly and nephromegaly. Severely affected infants present in the neonatal period with severe hypoglycemia due to fasting intolerance. More commonly, untreated infants present at age three to four months with hepatomegaly, severe hypoglycemia with or without seizures, lactic acidosis, hyperuricemia, and hypertriglyceridemia. Affected children typically have doll-like faces with full cheeks, relatively thin extremities, short stature, and a protuberant abdomen. Xanthoma and diarrhea may be present. Impaired platelet function and development of reduced or dysfunctional von Willebrand factor can lead to a bleeding tendency with frequent epistaxis and menorrhagia in females. Individuals with untreated GSDIb are more likely to develop impaired neutrophil and monocyte function as well as chronic neutropenia resulting in recurrent bacterial infections, gingivitis, periodontitis, and genital and intestinal ulcers. Long-term complications of untreated GSDI include short stature, osteoporosis, delayed puberty, renal disease (including proximal and distal renal tubular acidosis, renal stones, and renal failure), gout, systemic hypertension, pulmonary hypertension, hepatic adenomas with potential for malignancy, pancreatitis, and polycystic ovaries. Seizures and cognitive impairment may occur in individuals with prolonged periods of hypoglycemia. Normal growth and puberty are expected in treated children. Most affected individuals live into adulthood.

21-hydroxylase deficiency (21-OHD) is the most common cause of congenital adrenal hyperplasia (CAH), a family of autosomal recessive disorders involving impaired synthesis of cortisol from cholesterol by the adrenal cortex. In 21-OHD CAH, excessive adrenal androgen biosynthesis results in virilization in all individuals and salt wasting in some individuals. A classic form with severe enzyme deficiency and prenatal onset of virilization is distinguished from a non-classic form with mild enzyme deficiency and postnatal onset. The classic form is further divided into the simple virilizing form (~25% of affected individuals) and the salt-wasting form, in which aldosterone production is inadequate (=75% of individuals). Newborns with salt-wasting 21-OHD CAH are at risk for life-threatening salt-wasting crises. Individuals with the non-classic form of 21-OHD CAH present postnatally with signs of hyperandrogenism; females with the non-classic form are not virilized at birth.

Bardet-Biedl syndrome is an autosomal recessive and genetically heterogeneous ciliopathy characterized by retinitis pigmentosa, obesity, kidney dysfunction, polydactyly, behavioral dysfunction, and hypogonadism (summary by Beales et al., 1999). Eight proteins implicated in the disorder assemble to form the BBSome, a stable complex involved in signaling receptor trafficking to and from cilia (summary by Scheidecker et al., 2014). Genetic Heterogeneity of Bardet-Biedl Syndrome BBS2 (615981) is caused by mutation in a gene on 16q13 (606151); BBS3 (600151), by mutation in the ARL6 gene on 3q11 (608845); BBS4 (615982), by mutation in a gene on 15q22 (600374); BBS5 (615983), by mutation in a gene on 2q31 (603650); BBS6 (605231), by mutation in the MKKS gene on 20p12 (604896); BBS7 (615984), by mutation in a gene on 4q27 (607590); BBS8 (615985), by mutation in the TTC8 gene on 14q32 (608132); BBS9 (615986), by mutation in a gene on 7p14 (607968); BBS10 (615987), by mutation in a gene on 12q21 (610148); BBS11 (615988), by mutation in the TRIM32 gene on 9q33 (602290); BBS12 (615989), by mutation in a gene on 4q27 (610683); BBS13 (615990), by mutation in the MKS1 gene (609883) on 17q23; BBS14 (615991), by mutation in the CEP290 gene (610142) on 12q21, BBS15 (615992), by mutation in the WDPCP gene (613580) on 2p15; BBS16 (615993), by mutation in the SDCCAG8 gene (613524) on 1q43; BBS17 (615994), by mutation in the LZTFL1 gene (606568) on 3p21; BBS18 (615995), by mutation in the BBIP1 gene (613605) on 10q25; BBS19 (615996), by mutation in the IFT27 gene (615870) on 22q12; BBS20 (619471), by mutation in the IFT172 gene (607386) on 9p21; BBS21 (617406), by mutation in the CFAP418 gene (614477) on 8q22; and BBS22 (617119), by mutation in the IFT74 gene (608040) on 9p21. The CCDC28B gene (610162) modifies the expression of BBS phenotypes in patients who have mutations in other genes. Mutations in MKS1, MKS3 (TMEM67; 609884), and C2ORF86 also modify the expression of BBS phenotypes in patients who have mutations in other genes. Although BBS had originally been thought to be a recessive disorder, Katsanis et al. (2001) demonstrated that clinical manifestation of some forms of Bardet-Biedl syndrome requires recessive mutations in 1 of the 6 loci plus an additional mutation in a second locus. While Katsanis et al. (2001) called this 'triallelic inheritance,' Burghes et al. (2001) suggested the term 'recessive inheritance with a modifier of penetrance.' Mykytyn et al. (2002) found no evidence of involvement of the common BBS1 mutation in triallelic inheritance. However, Fan et al. (2004) found heterozygosity in a mutation of the BBS3 gene (608845.0002) as an apparent modifier of the expression of homozygosity of the met390-to-arg mutation in the BBS1 gene (209901.0001). Allelic disorders include nonsyndromic forms of retinitis pigmentosa: RP51 (613464), caused by TTC8 mutation, and RP55 (613575), caused by ARL6 mutation.

BBS2 is an autosomal recessive ciliopathy characterized by retinal degeneration, polydactyly, renal disease, hypogonadism, obesity, dysmorphic features, and variable degrees of cognitive impairment (Innes et al., 2010). Mutation in the BBS2 gene is the third most frequent cause of BBS, accounting for approximately 8% of cases (Zaghloul and Katsanis, 2009). For a general phenotypic description and a discussion of genetic heterogeneity of Bardet-Biedl syndrome, see BBS1 (209900).

Autosomal dominant polycystic kidney disease (ADPKD) is generally a late-onset multisystem disorder characterized by bilateral kidney cysts, liver cysts, and an increased risk of intracranial aneurysms. Other manifestations include: cysts in the pancreas, seminal vesicles, and arachnoid membrane; dilatation of the aortic root and dissection of the thoracic aorta; mitral valve prolapse; and abdominal wall hernias. Kidney manifestations include early-onset hypertension, kidney pain, and kidney insufficiency. Approximately 50% of individuals with ADPKD have end-stage kidney disease (ESKD) by age 60 years. The prevalence of liver cysts increases with age and occasionally results in clinically significant severe polycystic liver disease (PLD), most often in females. Overall, the prevalence of intracranial aneurysms is fivefold higher than in the general population and further increased in those with a positive family history of aneurysms or subarachnoid hemorrhage. There is substantial variability in the severity of kidney disease and other extra-kidney manifestations.

Cytochrome P450 oxidoreductase deficiency (PORD) is a disorder of steroidogenesis with a broad phenotypic spectrum including cortisol deficiency, altered sex steroid synthesis, disorders of sex development (DSD), and skeletal malformations of the Antley-Bixler syndrome (ABS) phenotype. Cortisol deficiency is usually partial, with some baseline cortisol production but failure to mount an adequate cortisol response in stress. Mild mineralocorticoid excess can be present and causes arterial hypertension, usually presenting in young adulthood. Manifestations of altered sex steroid synthesis include ambiguous genitalia/DSD in both males and females, large ovarian cysts in females, poor masculinization and delayed puberty in males, and maternal virilization during pregnancy with an affected fetus. Skeletal malformations can manifest as craniosynostosis, mid-face retrusion with proptosis and choanal stenosis or atresia, low-set dysplastic ears with stenotic external auditory canals, hydrocephalus, radiohumeral synostosis, neonatal fractures, congenital bowing of the long bones, joint contractures, arachnodactyly, and clubfeet; other anomalies observed include urinary tract anomalies (renal pelvic dilatation, vesicoureteral reflux). Cognitive impairment is of minor concern and likely associated with the severity of malformations; studies of developmental outcomes are lacking.

The nephronophthisis (NPH) phenotype is characterized by reduced renal concentrating ability, chronic tubulointerstitial nephritis, cystic renal disease, and progression to end-stage renal disease (ESRD) before age 30 years. Three age-based clinical subtypes are recognized: infantile, juvenile, and adolescent/adult. Infantile NPH can present in utero with oligohydramnios sequence (limb contractures, pulmonary hypoplasia, and facial dysmorphisms) or postnatally with renal manifestations that progress to ESRD before age 3 years. Juvenile NPH, the most prevalent subtype, typically presents with polydipsia and polyuria, growth retardation, chronic iron-resistant anemia, or other findings related to chronic kidney disease (CKD). Hypertension is typically absent due to salt wasting. ESRD develops at a median age of 13 years. Ultrasound findings are increased echogenicity, reduced corticomedullary differentiation, and renal cysts (in 50% of affected individuals). Histologic findings include tubulointerstitial fibrosis, thickened and disrupted tubular basement membrane, sporadic corticomedullary cysts, and normal or reduced kidney size. Adolescent/adult NPH is clinically similar to juvenile NPH, but ESRD develops at a median age of 19 years. Within a subtype, inter- and intrafamilial variability in rate of progression to ESRD is considerable. Approximately 80%-90% of individuals with the NPH phenotype have no extrarenal features (i.e., they have isolated NPH); ~10%-20% have extrarenal manifestations that constitute a recognizable syndrome (e.g., Joubert syndrome, Bardet-Biedl syndrome, Jeune syndrome and related skeletal disorders, Meckel-Gruber syndrome, Senior-Løken syndrome, Leber congenital amaurosis, COACH syndrome, and oculomotor apraxia, Cogan type).

Cranioectodermal dysplasia (CED) is a ciliopathy with skeletal involvement (narrow thorax, shortened proximal limbs, syndactyly, polydactyly, brachydactyly), ectodermal features (widely spaced hypoplastic teeth, hypodontia, sparse hair, skin laxity, abnormal nails), joint laxity, growth deficiency, and characteristic facial features (frontal bossing, low-set simple ears, high forehead, telecanthus, epicanthal folds, full cheeks, everted lower lip). Most affected children develop nephronophthisis that often leads to end-stage kidney disease in infancy or childhood, a major cause of morbidity and mortality. Hepatic fibrosis and retinal dystrophy are also observed. Dolichocephaly, often secondary to sagittal craniosynostosis, is a primary manifestation that distinguishes CED from most other ciliopathies. Brain malformations and developmental delay may also occur.

Smooth muscle dysfunction syndrome (SMDYS) presents with a recognizable pattern of complications, including congenital mydriasis, patent ductus arteriosus (PDA), pulmonary artery hypertension, aortic and other arterial aneurysms, moyamoya-like cerebrovascular disease, intestinal hypoperistalsis and malrotation, and hypotonic bladder. It is caused by heterozygous mutations of the ACTA2 gene altering the arginine-179 codon (summary by Regalado et al., 2018).

Nestor-Guillermo progeria syndrome (NGPS) is an autosomal recessive disorder characterized by lipoatrophy, osteoporosis, and very severe osteolysis. Patients have no cardiovascular impairment, diabetes mellitus, or hypertriglyceridemia, but suffer profound skeletal abnormalities that affect their quality of life. Onset is after 2 years of age, and lifespan is relatively long (summary by Cabanillas et al., 2011).

This multisystem disorder is characterized by moyamoya disease, short stature, hypergonadotropic hypogonadism, and facial dysmorphism. Other variable features include dilated cardiomyopathy, premature graying of the hair, and early-onset cataracts. Moyamoya disease is a progressive cerebrovascular disorder characterized by stenosis or occlusion of the internal carotid arteries and the main branches, leading to the development of small collateral vessels (moyamoya vessels) at the base of the brain. Affected individuals can develop acute neurologic events due to stroke-like episodes (summary by Miskinyte et al., 2011). For a general phenotypic description and a discussion of genetic heterogeneity of moyamoya disease, see MYMY1 (252350).

Generalized arterial calcification of infancy (GACI) is characterized by infantile onset of widespread arterial calcification and/or narrowing of large and medium-sized vessels resulting in cardiovascular findings (which can include heart failure, respiratory distress, edema, cyanosis, hypertension, and/or cardiomegaly). Additional findings can include typical skin and retinal manifestations of pseudoxanthoma elasticum (PXE), periarticular calcifications, development of rickets after infancy, cervical spine fusion, and hearing loss. While mortality in infancy is high, survival into the third and fourth decades has occurred.

Mitochondrial encephalo-cardio-myopathy due to <i>TMEM70</i> mutation is characterized by early neonatal onset of hypotonia, hypetrophic cardiomyopathy and apneic spells within hours after birth accompanied by lactic acidosis, hyperammonemia and 3-methylglutaconic aciduria.

Nephrotic syndrome type 5 (NPHS5) is an autosomal recessive disorder characterized by very early onset of progressive renal failure manifest as proteinuria with consecutive edema starting in utero or within the first 3 months of life. A subset of patients may develop mild ocular anomalies, such as myopia, nystagmus, and strabismus (summary by Hasselbacher et al., 2006). For a general phenotypic description and a discussion of genetic heterogeneity of nephrotic syndrome, see NPHS1 (256300).

Classic Joubert syndrome (JS) is characterized by three primary findings: A distinctive cerebellar and brain stem malformation called the molar tooth sign (MTS). Hypotonia. Developmental delays. Often these findings are accompanied by episodic tachypnea or apnea and/or atypical eye movements. In general, the breathing abnormalities improve with age, truncal ataxia develops over time, and acquisition of gross motor milestones is delayed. Cognitive abilities are variable, ranging from severe intellectual disability to normal. Additional findings can include retinal dystrophy, renal disease, ocular colobomas, occipital encephalocele, hepatic fibrosis, polydactyly, oral hamartomas, and endocrine abnormalities. Both intra- and interfamilial variation are seen.

Pseudohypoaldosteronism type II (PHAII) is characterized by hyperkalemia despite normal glomerular filtration rate (GFR) and frequently by hypertension. Other associated findings in both children and adults include hyperchloremia, metabolic acidosis, and suppressed plasma renin levels. Aldosterone levels are variable, but are relatively low given the degree of hyperkalemia (elevated serum potassium is a potent stimulus for aldosterone secretion). Hypercalciuria is well described.

Pseudohypoaldosteronism type II (PHAII) is characterized by hyperkalemia despite normal glomerular filtration rate (GFR) and frequently by hypertension. Other associated findings in both children and adults include hyperchloremia, metabolic acidosis, and suppressed plasma renin levels. Aldosterone levels are variable, but are relatively low given the degree of hyperkalemia (elevated serum potassium is a potent stimulus for aldosterone secretion). Hypercalciuria is well described.

Hereditary sensory and autonomic neuropathy type VI (HSAN6) is a severe autosomal recessive disorder characterized by neonatal hypotonia, respiratory and feeding difficulties, lack of psychomotor development, and autonomic abnormalities including labile cardiovascular function, lack of corneal reflexes leading to corneal scarring, areflexia, and absent axonal flare response after intradermal histamine injection (summary by Edvardson et al., 2012). For a discussion of genetic heterogeneity of hereditary sensory and autonomic neuropathy, see HSAN1 (162400).

Congenital disorder of glycosylation type IIm, or developmental and epileptic encephalopathy-22 (DEE22), is an X-linked dominant severe neurologic disorder characterized by infantile-onset seizures, hypsarrhythmia on EEG, hypotonia, and developmental delay associated with severe intellectual disability and lack of speech. These features are consistent with developmental and epileptic encephalopathy (DEE). Brain malformations usually include cerebral and cerebellar atrophy. Additionally, some patients may have dysmorphic features or coarse facies (Ng et al., 2013; Kodera et al., 2013). For a general discussion of CDGs, see CDG1A (212065) and CDG2A (212066). For a general phenotypic description and a discussion of genetic heterogeneity of DEE, see 308350.

Lipodystrophies are rare disorders characterized by loss of body fat from various regions and predisposition to metabolic complications of insulin resistance and lipid abnormalities. FPLD7 is an autosomal dominant disorder with a highly variable phenotype. Additional features, including early-onset cataracts and later onset of spasticity of the lower limbs, have been noted in some patients (summary by Garg et al., 2015). For a general phenotypic description and a discussion of genetic heterogeneity of familial partial lipodystrophy (FPLD), see 151660.

A rare genetic lipodystrophy with characteristics of abnormal subcutaneous fat distribution, resulting in preservation of visceral, neck and axillary fat and absence of lower limb and gluteofemoral subcutaneous fat. Additional clinical features are acanthosis nigricans, insulin-resistant type II diabetes mellitus, dyslipidaemia, and hypertension, leading to pancreatitis, hepatomegaly and hepatic steatosis.

Atrial fibrillation is the most common sustained cardiac rhythm disturbance, affecting more than 2 million Americans, with an overall prevalence of 0.89%. The prevalence increases rapidly with age, to 2.3% between the ages of 40 and 60 years, and to 5.9% over the age of 65. The most dreaded complication is thromboembolic stroke (Brugada et al., 1997). For a discussion of genetic heterogeneity of familial atrial fibrillation, see ATFB1 (608583).

A rare, genetic, neurologic disease characterized by primary hyperaldosteronism presenting with early-onset, severe hypertension, hypokalemia and neurological manifestations (including seizures, severe hypotonia, spasticity, cerebral palsy and profound developmental delay/intellectual disability).

A rare, genetic form of obesity characterized by morbid obesity, hypertension, type 2 diabetes mellitus and dyslipidemia leading to early coronary disease, myocardial infarction and congestive heart failure. Intellectual disability and decreased sperm counts or azoospermia have also been reported.

Moyamoya disease-6 (MYMY6) is a progressive vasculopathy characterized by occlusion of the terminal portion of the internal carotid arteries and its branches, and the formation of compensatory neovascularization and the moyamoya, or 'puff of smoke,' appearance of these vessels on angiogram. Affected individuals may present with ischemic strokes, intracerebral hemorrhage, or transient ischemic attacks. Patients with MYMY6 usually present early in life with achalasia. Hypertension and Raynaud phenomenon may be associated features (summary by Wallace et al., 2016; Herve et al., 2014). For a general phenotypic description and a discussion of genetic heterogeneity of moyamoya disease, see MYMY1 (252350).

Familial hyperaldosteronism type I (HALD1), also referred to as glucocorticoid-remediable aldosteronism (GRA), is an autosomal dominant disorder characterized by hypertension, variable hyperaldosteronism, and abnormal adrenal steroid production, including 18-oxocortisol and 18-hydroxycortisol (Lifton et al., 1992). There is significant phenotypic heterogeneity, and some individuals never develop hypertension (Stowasser et al., 2000). Genetic Heterogeneity of Familial Hyperaldosteronism Familial hyperaldosteronism type II (HALD2; 605635) is caused by mutation in the CLCN2 gene (600570) on chromosome 3q27. Familial hyperaldosteronism type III (HALD3; 613677) is caused by mutation in the KCNJ5 gene (600734) on chromosome 11q24. Familial hyperaldosteronism type IV (HALD4; 617027) is caused by mutation in the CACNA1H gene (607904) on chromosome 16p13.

Hyperaldosteronism type III (HALD3) is characterized by hypertension secondary to massive adrenal mineralocorticoid production. Like patients with glucocorticoid-remediable aldosteronism (GRA, or HALD1; 103900), patients with HALD3 present with childhood hypertension, elevated aldosteronism levels, and high levels of the hybrid steroids 18-oxocortisol and 18-hydroxycortisol. However, hypertension and aldosteronism in HALD3 are not reversed by administration of exogenous glucocorticoids and patients require adrenalectomy to control hypertension (Geller et al., 2008).

Adenosine deaminase 2 deficiency (DADA2) is a complex systemic autoinflammatory disorder in which vasculopathy/vasculitis, dysregulated immune function, and/or hematologic abnormalities may predominate. Inflammatory features include intermittent fevers, rash (often livedo racemosa/reticularis), and musculoskeletal involvement (myalgia/arthralgia, arthritis, myositis). Vasculitis, which usually begins before age ten years, may manifest as early-onset ischemic (lacunar) and/or hemorrhagic strokes, or as cutaneous or systemic polyarteritis nodosa. Hypertension and hepatosplenomegaly are often found. More severe involvement may lead to progressive central neurologic deficits (dysarthria, ataxia, cranial nerve palsies, cognitive impairment) or to ischemic injury to the kidney, intestine, and/or digits. Dysregulation of immune function can lead to immunodeficiency or autoimmunity of varying severity; lymphadenopathy may be present and some affected individuals have had lymphoproliferative disease. Hematologic disorders may begin early in life or in late adulthood, and can include lymphopenia, neutropenia, pure red cell aplasia, thrombocytopenia, or pancytopenia. Of note, both interfamilial and intrafamilial phenotypic variability (e.g., in age of onset, frequency and severity of manifestations) can be observed; also, individuals with biallelic ADA2 pathogenic variants may remain asymptomatic until adulthood or may never develop clinical manifestations of DADA2.

Autosomal dominant polycystic kidney disease (ADPKD) is generally a late-onset multisystem disorder characterized by bilateral kidney cysts, liver cysts, and an increased risk of intracranial aneurysms. Other manifestations include: cysts in the pancreas, seminal vesicles, and arachnoid membrane; dilatation of the aortic root and dissection of the thoracic aorta; mitral valve prolapse; and abdominal wall hernias. Kidney manifestations include early-onset hypertension, kidney pain, and kidney insufficiency. Approximately 50% of individuals with ADPKD have end-stage kidney disease (ESKD) by age 60 years. The prevalence of liver cysts increases with age and occasionally results in clinically significant severe polycystic liver disease (PLD), most often in females. Overall, the prevalence of intracranial aneurysms is fivefold higher than in the general population and further increased in those with a positive family history of aneurysms or subarachnoid hemorrhage. There is substantial variability in the severity of kidney disease and other extra-kidney manifestations.

Most characteristically, Aicardi-Goutières syndrome (AGS) manifests as an early-onset encephalopathy that usually, but not always, results in severe intellectual and physical disability. A subgroup of infants with AGS present at birth with abnormal neurologic findings, hepatosplenomegaly, elevated liver enzymes, and thrombocytopenia, a picture highly suggestive of congenital infection. Otherwise, most affected infants present at variable times after the first few weeks of life, frequently after a period of apparently normal development. Typically, they demonstrate the subacute onset of a severe encephalopathy characterized by extreme irritability, intermittent sterile pyrexias, loss of skills, and slowing of head growth. Over time, as many as 40% develop chilblain skin lesions on the fingers, toes, and ears. It is becoming apparent that atypical, sometimes milder, cases of AGS exist, and thus the true extent of the phenotype associated with pathogenic variants in the AGS-related genes is not yet known.

The nephronophthisis (NPH) phenotype is characterized by reduced renal concentrating ability, chronic tubulointerstitial nephritis, cystic renal disease, and progression to end-stage renal disease (ESRD) before age 30 years. Three age-based clinical subtypes are recognized: infantile, juvenile, and adolescent/adult. Infantile NPH can present in utero with oligohydramnios sequence (limb contractures, pulmonary hypoplasia, and facial dysmorphisms) or postnatally with renal manifestations that progress to ESRD before age 3 years. Juvenile NPH, the most prevalent subtype, typically presents with polydipsia and polyuria, growth retardation, chronic iron-resistant anemia, or other findings related to chronic kidney disease (CKD). Hypertension is typically absent due to salt wasting. ESRD develops at a median age of 13 years. Ultrasound findings are increased echogenicity, reduced corticomedullary differentiation, and renal cysts (in 50% of affected individuals). Histologic findings include tubulointerstitial fibrosis, thickened and disrupted tubular basement membrane, sporadic corticomedullary cysts, and normal or reduced kidney size. Adolescent/adult NPH is clinically similar to juvenile NPH, but ESRD develops at a median age of 19 years. Within a subtype, inter- and intrafamilial variability in rate of progression to ESRD is considerable. Approximately 80%-90% of individuals with the NPH phenotype have no extrarenal features (i.e., they have isolated NPH); ~10%-20% have extrarenal manifestations that constitute a recognizable syndrome (e.g., Joubert syndrome, Bardet-Biedl syndrome, Jeune syndrome and related skeletal disorders, Meckel-Gruber syndrome, Senior-Løken syndrome, Leber congenital amaurosis, COACH syndrome, and oculomotor apraxia, Cogan type).

Any metabolic syndrome in which the cause of the disease is a mutation in the DYRK1B gene.

Cushing syndrome is a clinical designation for the systemic signs and symptoms arising from excess cortisol production. Affected individuals typically show hypertension, impaired glucose tolerance, central obesity, osteoporosis, and sometimes depression. Corticotropin-independent Cushing syndrome results from autonomous cortisol production by the adrenal glands, often associated with adrenocortical tumors. Adrenocortical tumors are most common in adult females (summary by Cao et al., 2014; Sato et al., 2014).

ACTH-independent macronodular adrenal hyperplasia-2 is an autosomal dominant tumor susceptibility with syndromic incomplete penetrance, as a second hit to the ARMC5 gene is required to develop macronodular hyperplasia (Assie et al., 2013).

Familial partial lipodystrophy type 6 (FPLD6) is characterized by abnormal subcutaneous fat distribution, with variable excess accumulation of fat in the face, neck, shoulders, axillae, back, abdomen, and pubic region, and reduction in subcutaneous fat of the lower extremities. Progressive adult-onset myopathy is seen in some patients, and there is variable association with diabetes, hypertriglyceridemia, low high-density lipoprotein (HDL) cholesterol, and hepatic steatosis (Zolotov et al., 2017). For a general phenotypic description and a discussion of genetic heterogeneity of familial partial lipodystrophy (FPLD), see 151660.

Neonatal nephrocutaneous inflammatory syndrome (NNCIS) is an autosomal recessive disorder characterized by intrauterine growth retardation and premature birth, fragile infection-prone skin, and nephromegaly with tubular dysfunction. Some patients have chronic diarrhea, and necrotizing enterocolitis with intestinal perforation has been observed. Other features include facial dysmorphisms and cardiac anomalies. Most patients require ventilatory and circulatory support at birth, exhibit failure to thrive, experience recurrent infections with sepsis as a common complication, and die within 6 months (Mazurova et al., 2020; Labbouz et al., 2023). Reviews Takeichi and Akiyama (2021) reviewed published reports of patients with mutation in the EGFR gene, whose features included intrauterine growth restriction; thin, translucent, and fragile skin (14 of 15 cases); skin desquamation (10 of 17 cases); ichthyosis (9 of 17 cases); recurrent skin infections and sepsis (9 of 12 cases); nephromegaly (10 of 16 cases); and congenital heart defects (7 of 17 cases). Other observed features included erythroderma, tubulopathy, necrotizing enterocolitis/intestinal perforation, cryptorchidism, hyperimmunoglobulin E, and dentinogenesis imperfecta. Almost all children died within 2.5 years after birth. The authors suggested that EGFR-associated systemic inflammatory diseases should be considered a part of the clinical spectrum of 'autoinflammatory keratinization diseases' (AiKDs).

Any IgA glomerulonephritis in which the cause of the disease is a mutation in the SPRY2 gene.

HTRA1 disorder is a phenotypic spectrum in which some individuals have few to no symptoms and others manifest with the more severe CARASIL (cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy) phenotype. Those who have a heterozygous HTRA1 pathogenic variant may have mild neurologic findings (sometimes identified only on neuroimaging) or mild-to-moderate neurologic signs and symptoms of CARASIL. In this chapter, the term "classic CARASIL" refers to the more severe phenotype associated with biallelic pathogenic variants, and "HTRA1 cerebral small vessel disease" (HTRA1-CSVD) refers to the milder phenotype associated with a heterozygous HTRA1 pathogenic variant. Classic CARASIL is characterized by early-onset changes in the deep white matter of the brain observed on MRI, and associated neurologic findings. The most frequent initial symptom is gait disturbance from spasticity beginning between ages 20 and 40 years. Forty-four percent of affected individuals have stroke-like episodes before age 40 years. Mood changes (apathy and irritability), pseudobulbar palsy, and cognitive dysfunction begin between ages 20 and 50 years. The disease progresses slowly following the onset of neurologic symptoms. Scalp alopecia and acute mid- to lower-back pain (lumbago) before age 30 years are characteristic. The most frequent initial symptom in individuals with HTRA1-CSVD is slowly progressive gait disturbance after age 40 years, which may be followed by the development of mood changes and cognitive dysfunction. A majority of affected individuals have a stroke-like episode after age 40 years. Spondylosis and alopecia are seen in a minority of individuals with HTRA1-CSVD.

Primary coenzyme Q10 (CoQ10) deficiency is usually associated with multisystem involvement, including neurologic manifestations such as fatal neonatal encephalopathy with hypotonia; a late-onset slowly progressive multiple-system atrophy-like phenotype (neurodegeneration with autonomic failure and various combinations of parkinsonism and cerebellar ataxia, and pyramidal dysfunction); and dystonia, spasticity, seizures, and intellectual disability. Steroid-resistant nephrotic syndrome (SRNS), the hallmark renal manifestation, is often the initial manifestation either as isolated renal involvement that progresses to end-stage renal disease (ESRD), or associated with encephalopathy (seizures, stroke-like episodes, severe neurologic impairment) resulting in early death. Hypertrophic cardiomyopathy (HCM), retinopathy or optic atrophy, and sensorineural hearing loss can also be seen.

Au-Kline syndrome is characterized by developmental delay and hypotonia with moderate-to-severe intellectual disability, and typical facial features that include long palpebral fissures, ptosis, shallow orbits, large and deeply grooved tongue, broad nose with a wide nasal bridge, and downturned mouth. There is frequently variable autonomic dysfunction (gastrointestinal dysmotility, high pain threshold, heat intolerance, recurrent fevers, abnormal sweating). Congenital heart disease, hydronephrosis, palate abnormalities, and oligodontia are also reported in the majority of affected individuals. Additional complications can include craniosynostosis, feeding difficulty, vision issues, osteopenia, and other skeletal anomalies.

Any Seckel syndrome in which the cause of the disease is a mutation in the NSMCE2 gene.

Autosomal dominant tubulointerstitial kidney disease-5 (ADTKD5) is characterized by the onset of progressive chronic renal disease in the first decades of life. Mild hyperuricemia may be present, but gout, hypertension, and proteinuria are usually absent. The disease may be associated with anemia or neutropenia. Some patients may have additional findings, including poor overall growth and impaired cognitive function. Renal biopsy shows tubulointerstitial abnormalities with atrophic tubules and fibrosis; secondary glomerular abnormalities and simple cysts may also be present (summary by Bolar et al., 2016). For a discussion of genetic heterogeneity and revised nomenclature of ADTKD, see ADTKD1 (162000).

Hydrops, lactic acidosis, and sideroblastic anemia (HLASA) is an autosomal recessive multisystem disorder characterized by the onset of hydrops in utero. The severity of the hydrops and the disorder in general is highly variable. At birth, affected infants usually show poor growth, lactic acidosis, pulmonary hypertension with hypoxic respiratory insufficiency, and sideroblastic anemia. More variable features may include hepatosplenomegaly or cholestasis, hypoglycemia, pancreatic insufficiency, and micropenis or hypospadias. Death in infancy may occur. Those who survive tend to have resolution of lactic acidosis and anemia, but may show developmental delay and sensorineural deafness (summary by Riley et al., 2020).

The marfanoid-progeroid-lipodystrophy syndrome (MFLS) is characterized by congenital lipodystrophy, premature birth with an accelerated linear growth disproportionate to weight gain, and progeroid appearance with distinct facial features, including proptosis, downslanting palpebral fissures, and retrognathia. Other characteristic features include arachnodactyly, digital hyperextensibility, myopia, dural ectasia, and normal psychomotor development (Takenouchi et al., 2013). Takenouchi et al. (2013) noted phenotypic overlap with Marfan syndrome (154700) and Shprintzen-Goldberg craniosynostosis syndrome (182212).

AIP familial isolated pituitary adenoma (AIP-FIPA) is defined as the presence of an AIP germline pathogenic variant in an individual with a pituitary adenoma (regardless of family history). The most commonly occurring pituitary adenomas in this disorder are growth hormone-secreting adenomas (somatotropinoma), followed by prolactin-secreting adenomas (prolactinoma), growth hormone and prolactin co-secreting adenomas (somatomammotropinoma), and nonfunctioning pituitary adenomas (NFPA). Rarely TSH-secreting adenomas (thyrotropinomas) are observed. Clinical findings result from excess hormone secretion, lack of hormone secretion, and/or mass effects (e.g., headaches, visual field loss). Within the same family, pituitary adenomas can be of the same or different type. Age of onset in AIP-FIPA is usually in the second or third decade.

Birk-Landau-Perez syndrome (BILAPES) is an autosomal recessive syndromic developmental disorder characterized by global developmental delay apparent from infancy or early childhood. Some patients have developmental regression with loss of speech and motor skills, whereas other patients never achieve these milestones. More variable features may include hypotonia, poor overall growth, ataxia, dystonia, abnormal eye movements, and renal insufficiency (Perez et al., 2017; Kleyner et al., 2022).

PKD5, a form of autosomal recessive polycystic kidney disease (ARPKD), is characterized by early childhood onset of progressive renal dysfunction associated with enlarged hyperechogenic kidneys that often results in end-stage renal disease in the second or third decade of life. Arterial hypertension is apparent in early childhood (summary by Lu et al., 2017). For a discussion of genetic heterogeneity of polycystic kidney disease, see PKD1 (173900).

Galloway-Mowat syndrome is a renal-neurologic disease characterized by early-onset nephrotic syndrome associated with microcephaly, gyral abnormalities of the brain, and delayed psychomotor development. Most patients have dysmorphic facial features, often including hypertelorism, ear abnormalities, and micrognathia. Other features, such as arachnodactyly and visual impairment, are more variable. Most patients die in the first years of life (summary by Braun et al., 2017). For a general phenotypic description and a discussion of genetic heterogeneity of GAMOS, see GAMOS1 (251300).

SHRF is an autosomal recessive disorder characterized by short stature, brachydactyly, dysmorphic facial features, hearing loss, and visual impairment. Onset of the hearing and visual abnormalities, including retinitis pigmentosa, varies from birth to the second decade. Patients have mild intellectual disability and mild cerebellar atrophy with myelination defects on brain imaging (summary by Di Donato et al., 2016).

Autosomal recessive polycystic kidney disease (ARPKD) belongs to a group of congenital hepatorenal fibrocystic syndromes and is a cause of significant renal and liver-related morbidity and mortality in children. The majority of individuals with ARPKD present in the neonatal period with enlarged echogenic kidneys. Renal disease is characterized by nephromegaly, hypertension, and varying degrees of renal dysfunction. More than 50% of affected individuals with ARPKD progress to end-stage renal disease (ESRD) within the first decade of life; ESRD may require kidney transplantation. Pulmonary hypoplasia resulting from oligohydramnios occurs in a number of affected infants. Approximately 30% of these infants die in the neonatal period or within the first year of life from respiratory insufficiency or superimposed pulmonary infections. With neonatal respiratory support and renal replacement therapies, the long-term survival of these infants has improved to greater than 80%. As advances in renal replacement therapy and kidney transplantation improve long-term survival, it is likely that clinical hepatobiliary disease will become a major feature of the natural history of ARPKD. In addition, a subset of individuals with this disorder are identified with hepatosplenomegaly; the renal disease is often mild and may be discovered incidentally during imaging studies of the abdomen. Approximately 50% of infants will have clinical evidence of liver involvement at diagnosis although histologic hepatic fibrosis is invariably present at birth. This can lead to progressive portal hypertension with resulting esophageal or gastric varices, enlarged hemorrhoids, splenomegaly, hypersplenism, protein-losing enteropathy, and gastrointestinal bleeding. Other hepatic findings include nonobstructed dilatation of the intrahepatic bile ducts (Caroli syndrome) and dilatation of the common bile duct, which may lead to recurrent or persistent bacterial ascending cholangitis due to dilated bile ducts and stagnant bile flow. An increasing number of affected individuals surviving the neonatal period will eventually require portosystemic shunting or liver transplantation for complications of portal hypertension or cholangitis. The classic neonatal presentation of ARPKD notwithstanding, there is significant variability in age and presenting clinical symptoms related to the relative degree of renal and biliary abnormalities.

Adams-Oliver syndrome (AOS) is characterized by aplasia cutis congenita (ACC) of the scalp and terminal transverse limb defects (TTLD). ACC lesions usually occur in the midline of the parietal or occipital regions, but can also occur on the abdomen or limbs. At birth, an ACC lesion may already have the appearance of a healed scar. ACC lesions less than 5 cm often involve only the skin and almost always heal over a period of months; larger lesions are more likely to involve the skull and possibly the dura, and are at greater risk for complications, which can include infection, hemorrhage, or thrombosis, and can result in death. The limb defects range from mild (unilateral or bilateral short distal phalanges) to severe (complete absence of all toes or fingers, feet or hands, or more, often resembling an amputation). The lower extremities are almost always more severely affected than the upper extremities. Additional major features frequently include cardiovascular malformations/dysfunction (23%), brain anomalies, and less frequently renal, liver, and eye anomalies.

Autosomal dominant tubulointerstitial kidney disease – UMOD (ADTKD-UMOD) is characterized by normal urinalysis and slowly progressive chronic kidney disease (CKD), usually first noted in the teen years and progressing to end-stage renal disease (ESRD) between the third and seventh decades. Hyperuricemia is often present from an early age, and gout (resulting from reduced kidney excretion of uric acid) occurs in the teenage years in about 8% of affected individuals and develops in 55% of affected individuals over time.

Focal segmental glomerulosclerosis (FSGS) is a pathologic finding in several renal disorders that manifest clinically as proteinuria and progressive decline in renal function. Some patients with FSGS develop the clinical entity called 'nephrotic syndrome' (see NPHS1; 256300), which includes massive proteinuria, hypoalbuminemia, hyperlipidemia, and edema. However, patients with FSGS may have proteinuria in the nephrotic range without other features of the nephrotic syndrome (summary by D'Agati et al., 2004; Mathis et al., 1998). D'Agati et al. (2011) provided a detailed review of FSGS, emphasizing that the disorder results from defects of the podocyte. Because of confusion in the literature regarding use of the terms 'nephrotic syndrome' and 'focal segmental glomerulosclerosis' (see NOMENCLATURE section), these disorders in OMIM are classified as NPHS or FSGS according to how they were first designated in the literature. Genetic Heterogeneity of Focal Segmental Glomerulosclerosis and Nephrotic Syndrome Focal segmental glomerulosclerosis and nephrotic syndrome are genetically heterogeneous disorders representing a spectrum of hereditary renal diseases. See also FSGS2 (603965), caused by mutation in the TRPC6 gene (603652); FSGS3 (607832), associated with variation in the CD2AP gene (604241); FSGS4 (612551), mapped to chromosome 22q12; FSGS5 (613237), caused by mutation in the INF2 gene (610982); FSGS6 (614131), caused by mutation in the MYO1E gene (601479); FSGS7 (616002), caused by mutation in the PAX2 gene (167409); FSGS8 (616032), caused by mutation in the ANLN gene (616027); FSGS9 (616220), caused by mutation in the CRB2 gene (609720); and FSGS10 (256020), caused by mutation in the LMX1B gene (602575). See also NPHS1 (256300), caused by mutation in the NPHS1 gene (602716); NPHS2 (600995), caused by mutation in the podocin gene (604766); NPHS3 (610725), caused by mutation in the PLCE1 gene (608414); NPHS4 (256370), caused by mutation in the WT1 gene (607102); NPHS5 (614199), caused by mutation in the LAMB2 gene (150325); NPHS6 (614196), caused by mutation in the PTPRO gene (600579); NPHS7 (615008), caused by mutation in the DGKE gene (601440); NPHS8 (615244), caused by mutation in the ARHGDIA gene (601925); NPHS9 (615573), caused by mutation in the COQ8B gene (615567); NPHS10 (615861), caused by mutation in the EMP2 gene (602334); NPHS11 (616730), caused by mutation in the NUP107 gene (607617); NPHS12 (616892), caused by mutation in the NUP93 gene (614351); NPHS13 (616893), caused by mutation in the NUP205 gene (614352); NPHS14 (617575), caused by mutation in the SGPL1 gene (603729); NPHS15 (617609), caused by mutation in the MAGI2 gene (606382); NPHS16 (617783), caused by mutation in the KANK2 gene (614610), NPHS17 (618176), caused by mutation in the NUP85 gene (170285); NPHS18 (618177), caused by mutation in the NUP133 gene (607613); NPHS19 (618178), caused by mutation in the NUP160 gene (607614); NPHS20 (301028), caused by mutation in the TBC1D8B gene (301027); and NPHS21 (618594) caused by mutation in the AVIL gene (613397).

Primary familial and congenital polycythemia (PFCP) is characterized by isolated erythrocytosis in an individual with a normal-sized spleen and absence of disorders causing secondary erythrocytosis. Clinical manifestations relate to the erythrocytosis and can include plethora, the hyperviscosity syndrome (headache, dizziness, fatigue, lassitude, visual and auditory disturbances, paresthesia, myalgia), altered mental status caused by hypoperfusion and local hypoxia, and arterial and/or venous thromboembolic events. Although the majority of individuals with PFCP have only mild manifestations of hyperviscosity such as dizziness or headache, some affected individuals have had severe and even fatal complications including arterial hypertension, intracerebral hemorrhage, deep vein thrombosis, coronary disease, and myocardial infarction. To date 116 affected individuals from 24 families have been reported.

Generalized arterial calcification of infancy (GACI) is characterized by infantile onset of widespread arterial calcification and/or narrowing of large and medium-sized vessels resulting in cardiovascular findings (which can include heart failure, respiratory distress, edema, cyanosis, hypertension, and/or cardiomegaly). Additional findings can include typical skin and retinal manifestations of pseudoxanthoma elasticum (PXE), periarticular calcifications, development of rickets after infancy, cervical spine fusion, and hearing loss. While mortality in infancy is high, survival into the third and fourth decades has occurred.

A clustering of abdominal obesity, high triglycerides, low levels of high density lipoprotein cholesterol (HDLC), high blood pressure, and elevated fasting glucose levels is sometimes called metabolic syndrome X (Reaven, 1988) or abdominal obesity-metabolic syndrome (Bjorntorp, 1991). The syndrome may affect nearly 1 in 4 U.S. adults and is considered a veritable epidemic (Ford et al., 2002). It is a major risk factor for both diabetes mellitus (see 125853 and Haffner et al., 1992) and cardiovascular disease (Isomaa et al., 2001). The etiology is complex, determined by the interplay of both genetic and environmental factors. The prevalence varies substantially among ethnic groups, with the highest rates in Mexican American women (Park et al., 2003). Other factors influencing the metabolic syndrome include age, smoking, alcohol, diet, and physical inactivity. Genetic Heterogeneity of Abdominal Obesity-Metabolic Syndrome AOMS2 (605572) has been mapped to chromosome 17p12. AOMS3 (615812) is caused by mutation in the DYRK1B gene (604556) on chromosome 19q13. AOMS4 (618620) is caused by mutation in the CELA2A gene (609443) on chromosome 1p36.

Primary pulmonary arterial hypertension is a rare, often fatal, progressive vascular lung disease characterized by increased pulmonary vascular resistance and sustained elevation of mean pulmonary arterial pressure, leading to right ventricular hypertrophy and right heart failure. Pathologic features include a narrowing and thickening of small pulmonary vessels and plexiform lesions. There is pulmonary vascular remodeling of all layers of pulmonary arterial vessels: intimal thickening, smooth muscle cell hypertrophy or hyperplasia, adventitial fibrosis, and occluded vessels by in situ thrombosis (summary by Machado et al., 2009 and Han et al., 2013). Heterozygous mutations in the BMPR2 gene are found in nearly 70% of families with heritable PPH and in 25% of patients with sporadic disease. The disease is more common in women (female:male ratio of 1.7:1). However, the penetrance of PPH1 is incomplete: only about 10 to 20% of individuals with BMPR2 mutations develop the disease during their lifetime, suggesting that development of the disorder is triggered by other genetic or environmental factors. Patients with PPH1 are less likely to respond to acute vasodilater testing and are unlikely to benefit from treatment with calcium channel blockade (summary by Machado et al., 2009 and Han et al., 2013). Genetic Heterogeneity of Primary Pulmonary Hypertension See also PPH2 (615342), caused by mutation in the SMAD9 gene (603295) on chromosome 13q13; PPH3 (615343), caused by mutation in the CAV1 gene (601047) on chromosome 7q31; PPH4 (615344), caused by mutation in the KCNK3 gene (603220) on chromosome 2p23; PPH5 (265400), caused by mutation in the ATP13A3 gene (610232) on chromosome 3q29; and PPH6 (620777), caused by mutation in the CAPNS1 gene (114170) on chromosome 19q13. Primary pulmonary hypertension may also be found in association with hereditary hemorrhagic telangiectasia type 1 (HHT1; 187300), caused by mutation in the ENG gene (131195), and HHT2 (600376), caused by mutation in the ACVRL1 (ALK1) gene (601284). Pediatric-onset pulmonary hypertension may be seen in association with ischiocoxopodopatellar syndrome (ICPPS; 147891). The skeletal manifestations of ICPPS are highly variable and may not be detected in children. Parents are not likely to have PAH (Levy et al., 2016).

A rare mitochondrial disease due to a defect in mitochondrial protein synthesis with onset in infancy or early childhood of muscular hypotonia, gait ataxia, mild bilateral pyramidal tract signs, developmental delay (affecting mostly speech and coordination) and subsequent intellectual disability. Short stature, obesity, microcephaly, strabismus, nystagmus, reduced visual acuity, lactic acidosis, and a brain neuropathology consistent with Leigh syndrome are also reported. Caused by homozygous or compound heterozygous mutation in the MTFMT gene on chromosome 15q22.

In Alport syndrome (AS) a spectrum of phenotypes ranging from progressive renal disease with extrarenal abnormalities to isolated hematuria with a non-progressive or very slowly progressive course is observed. Approximately two thirds of AS is X-linked (XLAS); approximately 15% is autosomal recessive (ARAS), and approximately 20% is autosomal dominant (ADAS). In the absence of treatment, renal disease progresses from microscopic hematuria (microhematuria) to proteinuria, progressive renal insufficiency, and end-stage renal disease (ESRD) in all males with XLAS, and in all males and females with ARAS. Progressive sensorineural hearing loss (SNHL) is usually present by late childhood or early adolescence. Ocular findings include anterior lenticonus (which is virtually pathognomonic), maculopathy (whitish or yellowish flecks or granulations in the perimacular region), corneal endothelial vesicles (posterior polymorphous dystrophy), and recurrent corneal erosion. In individuals with ADAS, ESRD is frequently delayed until later adulthood, SNHL is relatively late in onset, and ocular involvement is rare.

In Alport syndrome (AS) a spectrum of phenotypes ranging from progressive renal disease with extrarenal abnormalities to isolated hematuria with a non-progressive or very slowly progressive course is observed. Approximately two thirds of AS is X-linked (XLAS); approximately 15% is autosomal recessive (ARAS), and approximately 20% is autosomal dominant (ADAS). In the absence of treatment, renal disease progresses from microscopic hematuria (microhematuria) to proteinuria, progressive renal insufficiency, and end-stage renal disease (ESRD) in all males with XLAS, and in all males and females with ARAS. Progressive sensorineural hearing loss (SNHL) is usually present by late childhood or early adolescence. Ocular findings include anterior lenticonus (which is virtually pathognomonic), maculopathy (whitish or yellowish flecks or granulations in the perimacular region), corneal endothelial vesicles (posterior polymorphous dystrophy), and recurrent corneal erosion. In individuals with ADAS, ESRD is frequently delayed until later adulthood, SNHL is relatively late in onset, and ocular involvement is rare.

Autosomal dominant polycystic kidney disease (ADPKD) is generally a late-onset multisystem disorder characterized by bilateral kidney cysts, liver cysts, and an increased risk of intracranial aneurysms. Other manifestations include: cysts in the pancreas, seminal vesicles, and arachnoid membrane; dilatation of the aortic root and dissection of the thoracic aorta; mitral valve prolapse; and abdominal wall hernias. Kidney manifestations include early-onset hypertension, kidney pain, and kidney insufficiency. Approximately 50% of individuals with ADPKD have end-stage kidney disease (ESKD) by age 60 years. The prevalence of liver cysts increases with age and occasionally results in clinically significant severe polycystic liver disease (PLD), most often in females. Overall, the prevalence of intracranial aneurysms is fivefold higher than in the general population and further increased in those with a positive family history of aneurysms or subarachnoid hemorrhage. There is substantial variability in the severity of kidney disease and other extra-kidney manifestations.

Liddle syndrome is an autosomal dominant form of hypertension characterized by early onset of hypertension associated with hypokalemia, suppressed plasma renin activity, and suppressed secretion of the mineralocorticoid hormone aldosterone (summary by Hansson et al., 1995). For a general phenotypic description and a discussion of genetic heterogeneity of Liddle syndrome, see 177200.

Liddle syndrome, or pseudoaldosteronism, is an autosomal dominant form of salt-sensitive hypertension characterized by suppressed plasma renin and aldosterone, hypokalemia, and metabolic alkalosis (summary by Salih et al., 2017). For a discussion of genetic heterogeneity of Liddle syndrome, see 177200.

Familial partial lipodystrophy type 4 is an autosomal dominant metabolic disorder characterized by childhood or young adult onset of loss of subcutaneous adipose tissue primarily affecting the lower limbs, insulin-resistant diabetes mellitus, hypertriglyceridemia, and hypertension (summary by Gandotra et al., 2011). Other features may include hepatic steatosis, acanthosis nigricans, polycystic ovary syndrome, and renal disease (summary by Chen et al., 2018). For a general phenotypic description and a discussion of genetic heterogeneity of familial partial lipodystrophy (FPLD), see 151660.

Pheochromocytoma/paraganglioma syndrome-6 (PPGL6) is an autosomal dominant adult-onset tumor predisposition syndrome in which affected individuals develop neuroendocrine neoplasms, known as paragangliomas. Many tumors arise in the abdomen, although some may arise in other regions, including the head and neck. Some of the tumors may secrete biologically active normetanephrines, resulting in secondary hypertension. Tumors may be benign or malignant, and some may metastasize (summary by Buffet et al., 2018). For a discussion of genetic heterogeneity of pheochromocytoma/paraganglioma syndrome, see PPGL1 (168000).

Blau syndrome is characterized by the triad of granulomatous arthritis, uveitis, and dermatitis. First described in 1985, it was considered to be distinct from sarcoidosis due to the early age of onset and autosomal dominant inheritance pattern. Published reports of sporadic cases of children with 'early-onset sarcoidosis' (EOS) with granulomatous involvement of different organs, primarily affecting joints, eyes, and skin, were suspected to represent the same disorder because the patients' characteristics were nearly identical. Subsequently, identical NOD2 mutations were identified in patients with Blau syndrome as well as in patients diagnosed with EOS, confirming earlier suspicions that they represented the same disease (summary by Borzutzky et al., 2010). Unlike older children diagnosed with sarcoidosis, these patients have no apparent pulmonary involvement; however, the disease is progressive and may result in severe complications such as blindness and/or joint destruction (Shetty and Gedalia, 1998).

Abdominal obesity-metabolic syndrome-4 (AOMS4) is characterized by obesity, hypertension, and early-onset coronary artery disease. Most affected individuals meet the criteria for metabolic syndrome, including elevated triglyceride and low high-density lipoprotein levels, and type 2 diabetes (Esteghamat et al., 2019). For a discussion of the genetic heterogeneity of abdominal obesity-metabolic syndrome, see AOMS1 (605552).

Lessel-Kubisch syndrome (LSKB) is characterized by short stature and progeroid features, including prematurely gray hair, pinched facies, and scleroderma-like skin changes. Renal failure-associated hypertension and hypogonadism have also been observed (Lessel et al., 2017).

Pseudo-TORCH syndrome-3 (PTORCH3) is an autosomal recessive disorder of immune dysregulation and neuroinflammation apparent from early infancy. Affected individuals have developmental delay with acute episodes of fever and multisystemic organ involvement, including coagulopathy, elevated liver enzymes, and proteinuria, often associated with thrombotic microangiopathy. Brain imaging shows progressive intracranial calcifications, white matter abnormalities, and sometimes cerebral or cerebellar atrophy. Laboratory studies show abnormal elevation of interferon (IFN)-stimulated gene (ISG) transcripts consistent with a type I interferonopathy. The phenotype resembles the sequelae of intrauterine infection, but there is usually no evidence of an infectious agent. The disorder results from defects in negative regulation of the interferon immunologic pathway. Death in early childhood is common (summary by Duncan et al., 2019 and Gruber et al., 2020). For a discussion of genetic heterogeneity of PTORCH, see PTORCH1 (251290).

Fanconi renotubular syndrome-5 (FRTS5) is a mitochondrial disorder characterized by proximal renotubular dysfunction from birth, followed by progressive kidney disease and pulmonary fibrosis. It occurs only in individuals of Acadian descent (Crocker et al., 1997 and Hartmannova et al., 2016). For a discussion of genetic heterogeneity of Fanconi renotubular syndrome, see FRTS1 (134600).

The IFAP/BRESHECK syndrome is an X-linked multiple congenital anomaly disorder with variable severity. The classic triad, which defines IFAP, is ichthyosis follicularis, atrichia, and photophobia. Some patients have additional features, including mental retardation, brain anomalies, Hirschsprung disease, corneal opacifications, kidney dysplasia, cryptorchidism, cleft palate, and skeletal malformations, particularly of the vertebrae, which constitutes BRESHECK syndrome (summary by Naiki et al., 2012). Genetic Heterogeneity of IFAP Syndrome IFAP syndrome-2 (IFAP2; 619016) is caused by heterozygous mutation in the SREBF1 gene (184756) on chromosome 17p11.

Any COACH syndrome in which the cause of the disease is a variation in the TMEM67 gene.

COACH syndrome is classically defined as Cerebellar vermis hypoplasia, Oligophrenia, Ataxia, Colobomas, and Hepatic fibrosis (Verloes and Lambotte, 1989). Brain MRI demonstrates the molar tooth sign, which is a feature of Joubert syndrome. The disorder has been described as a Joubert syndrome-related disorder with liver disease (summary by Doherty et al., 2010). For a general phenotypic description and a discussion of genetic heterogeneity of COACH syndrome, see 216360.

Aicardi-Goutieres syndrome-9 (AGS9) is a type I interferonopathy characterized by severe developmental delay and progressive neurologic deterioration. Patients present in infancy with irritability and spasticity. Brain imaging shows diffusely abnormal white matter, cerebral atrophy, and intracranial calcification. Premature death has been associated with renal and/or hepatic failure (Uggenti et al., 2020). For a general phenotypic description and discussion of genetic heterogeneity of Aicardi-Goutieres syndrome, see AGS1 (225750).

Immunodeficiency-87 and autoimmunity (IMD87) is an autosomal recessive immunologic disorder with wide phenotypic variation and severity. Affected individuals usually present in infancy or early childhood with increased susceptibility to infections, often Epstein-Barr virus (EBV), as well as with lymphadenopathy or autoimmune manifestations, predominantly hemolytic anemia. Laboratory studies may show low or normal lymphocyte numbers, often with skewed T-cell subset ratios. The disorder results primarily from defects in T-cell function, which causes both immunodeficiency and overall immune dysregulation (summary by Serwas et al., 2019 and Fournier et al., 2021).

Preeclampsia, which along with chronic hypertension and gestational hypertension comprise the hypertensive disorders of pregnancy, is characterized by new hypertension (blood pressure 140/90 or greater) presenting after 20 weeks' gestation with clinically relevant proteinuria. Preeclampsia is 1 of the top 4 causes of maternal mortality and morbidity worldwide (summary by Payne et al., 2011). Preeclampsia is otherwise known as gestational proteinuric hypertension (Davey and MacGillivray, 1988). A high proportion of patients with preeclampsia have glomerular endotheliosis, the unique histopathologic feature of the condition (Fisher et al., 1981). A distinct form of severe preeclampsia is characterized by hemolysis, elevated liver enzymes, and low platelets (HELLP syndrome) (Brown et al., 2000). Genetic Heterogeneity of Preeclampsia/Eclampsia Susceptibility loci for preeclampsia/eclampsia include PEE1 on chromosome 2p13, PEE2 (609402) on chromosome 2p25, and PEE3 (609403) on chromosome 9p13. PEE4 (609404) is caused by mutation in the STOX1 gene (609397) on chromosome 10q22. PEE5 (614595) is caused by mutation in the CORIN gene (605236) on chromosome 4p12. An association with PEE has been found with the EPHX1 gene (132810) on chromosome 1q.

Tessadori-Bicknell-van Haaften neurodevelopmental syndrome-1 (TEBIVANED1) is characterized by poor overall growth with short stature, microcephaly, hypotonia, profound global developmental delay often with poor or absent speech, and characteristic dysmorphic facial features, including hypertelorism and abnormal nose. Other variable neurologic and systemic features may also occur (Tessadori et al., 2017). Genetic Heterogeneity of Tessadori-van Haaften Neurodevelopmental Syndrome See also TEBIVANED2 (619759), caused by mutation in the H4C11 gene (602826); TEBIVANED3 (619950), caused by mutation in the H4C5 gene (602830); and TEBIVANED4 (619951), caused by mutation in the H4C9 gene (602833).

Autosomal dominant polycystic kidney disease (ADPKD) is generally a late-onset multisystem disorder characterized by bilateral kidney cysts, liver cysts, and an increased risk of intracranial aneurysms. Other manifestations include: cysts in the pancreas, seminal vesicles, and arachnoid membrane; dilatation of the aortic root and dissection of the thoracic aorta; mitral valve prolapse; and abdominal wall hernias. Kidney manifestations include early-onset hypertension, kidney pain, and kidney insufficiency. Approximately 50% of individuals with ADPKD have end-stage kidney disease (ESKD) by age 60 years. The prevalence of liver cysts increases with age and occasionally results in clinically significant severe polycystic liver disease (PLD), most often in females. Overall, the prevalence of intracranial aneurysms is fivefold higher than in the general population and further increased in those with a positive family history of aneurysms or subarachnoid hemorrhage. There is substantial variability in the severity of kidney disease and other extra-kidney manifestations.

In Alport syndrome (AS) a spectrum of phenotypes ranging from progressive renal disease with extrarenal abnormalities to isolated hematuria with a non-progressive or very slowly progressive course is observed. Approximately two thirds of AS is X-linked (XLAS); approximately 15% is autosomal recessive (ARAS), and approximately 20% is autosomal dominant (ADAS). In the absence of treatment, renal disease progresses from microscopic hematuria (microhematuria) to proteinuria, progressive renal insufficiency, and end-stage renal disease (ESRD) in all males with XLAS, and in all males and females with ARAS. Progressive sensorineural hearing loss (SNHL) is usually present by late childhood or early adolescence. Ocular findings include anterior lenticonus (which is virtually pathognomonic), maculopathy (whitish or yellowish flecks or granulations in the perimacular region), corneal endothelial vesicles (posterior polymorphous dystrophy), and recurrent corneal erosion. In individuals with ADAS, ESRD is frequently delayed until later adulthood, SNHL is relatively late in onset, and ocular involvement is rare.

Developmental and epileptic encephalopathy-111 (DEE111) is an autosomal recessive severe neurologic disorder characterized by early-onset refractory seizures, global developmental delay, hypotonia, impaired gross motor development, impaired intellectual development, and absent speech. Most patients have macrocephaly. Brain imaging shows frontal, parietal, and perisylvian polymicrogyria, dysmorphic basal ganglia and corpus callosum, and hypoplastic pons. Additional features may include feeding difficulties, poor vision with ocular anomalies, congenital cardiac abnormalities, and recurrent infections associated with neutropenia. Death in early childhood may occur (Ververi et al., 2023). For a discussion of genetic heterogeneity of DEE, see 308350.

Familial partial lipodystrophy type 8 (FPLD8) is an autosomal dominant disorder characterized by abnormal distribution of subcutaneous adipose tissue. Affected individuals showed selective loss of subcutaneous adipose tissue from the limbs, resulting in a muscular appearance, beginning around 13 to 15 years of age. There is also abnormal accumulation of subcutaneous adipose tissue in the dorsal neck and face, as well as in the posterior thoracic and abdominal regions. The disorder is associated with metabolic abnormalities, including diabetes mellitus and hyperlipidemia (Garg et al., 2016). For a general description and a discussion of genetic heterogeneity of familial partial lipodystrophy (FPLD), see 151660.

Familial partial lipodystrophy type 9 (FPLD9) is an autosomal recessive metabolic disorder characterized by the loss of adipose tissue resulting in a lean appearance with muscular hypertrophy, usually most apparent in the limbs and trunk. Some patients have more generalized lipoatrophy, whereas others have abnormal fat accumulation in the face and neck regions and show cushingoid or acromegalic facial features. The disorder is associated with insulin-resistant diabetes mellitus, dyslipidemia, low HDL, and hepatic steatosis. Symptom onset is usually in the first decade. Females tend to have hirsutism and polycystic ovary syndrome, whereas males have gynecomastia. Most patients also have neurologic involvement, including demyelinating polyneuropathy (in most) and delayed development with intellectual disability (in about half) (Schuermans et al., 2023). For a discussion of genetic heterogeneity of familial partial lipodystrophy (FPLD), see 151660.