Deficiency of lysosomal acid lipase causes 2 distinct phenotypes in humans: Wolman disease (WOLD; 620151) and cholesteryl ester storage disease (CESD). WOLD is an early-onset fulminant disorder of infancy with massive infiltration of the liver, spleen, and other organs by macrophages filled with cholesteryl esters and triglycerides. Death occurs early in life. CESD is a milder, later-onset disorder with primary hepatic involvement by macrophages engorged with cholesteryl esters. This slowly progressive visceral disease has a wide spectrum of involvement ranging from early onset with severe cirrhosis to later onset of more slowly progressive hepatic disease with survival into adulthood (summary by Du et al., 2001).

Cystic fibrosis (CF) is a multisystem disease affecting epithelia of the respiratory tract, exocrine pancreas, intestine, hepatobiliary system, and exocrine sweat glands. Morbidities include recurrent sinusitis and bronchitis, progressive obstructive pulmonary disease with bronchiectasis, exocrine pancreatic deficiency and malnutrition, pancreatitis, gastrointestinal manifestations (meconium ileus, rectal prolapse, distal intestinal obstructive syndrome), liver disease, diabetes, male infertility due to hypoplasia or aplasia of the vas deferens, and reduced fertility or infertility in some women. Pulmonary disease is the major cause of morbidity and mortality in CF.

Autoimmune polyendocrine syndrome type II (APS2), or Schmidt syndrome, is characterized by the presence of autoimmune Addison disease in association with either autoimmune thyroid disease or type I diabetes mellitus, or both. Chronic candidiasis is not present. APS2 may occur at any age and in both sexes, but is most common in middle-aged females and is very rare in childhood (summary by Betterle et al., 2004). See 240300 for a phenotypic description of autoimmune polyendocrine syndrome type I (APS1).

PRSS1-related hereditary pancreatitis (HP) is characterized by episodes of acute pancreatitis (AP) and recurrent acute pancreatitis (RAP: >1 episode of AP), with frequent progression to chronic pancreatitis (CP). Manifestations of acute pancreatitis can range from vague abdominal pain lasting one to three days to severe abdominal pain lasting days to weeks and requiring hospitalization.

Mitochondrial DNA (mtDNA) deletion syndromes predominantly comprise three overlapping phenotypes that are usually simplex (i.e., a single occurrence in a family), but rarely may be observed in different members of the same family or may evolve from one clinical syndrome to another in a given individual over time. The three classic phenotypes caused by mtDNA deletions are Kearns-Sayre syndrome (KSS), Pearson syndrome, and progressive external ophthalmoplegia (PEO). KSS is a progressive multisystem disorder defined by onset before age 20 years, pigmentary retinopathy, and PEO; additional features include cerebellar ataxia, impaired intellect (intellectual disability, dementia, or both), sensorineural hearing loss, ptosis, oropharyngeal and esophageal dysfunction, exercise intolerance, muscle weakness, cardiac conduction block, and endocrinopathy. Pearson syndrome is characterized by sideroblastic anemia and exocrine pancreas dysfunction and may be fatal in infancy without appropriate hematologic management. PEO is characterized by ptosis, impaired eye movements due to paralysis of the extraocular muscles (ophthalmoplegia), oropharyngeal weakness, and variably severe proximal limb weakness with exercise intolerance. Rarely, a mtDNA deletion can manifest as Leigh syndrome.

PMM2-CDG, the most common of a group of disorders of abnormal glycosylation of N-linked oligosaccharides, is divided into three clinical stages: infantile multisystem, late-infantile and childhood ataxia–intellectual disability, and adult stable disability. The clinical manifestations and course are highly variable, ranging from infants who die in the first year of life to mildly affected adults. Clinical findings tend to be similar in sibs. In the infantile multisystem presentation, infants show axial hypotonia, hyporeflexia, esotropia, and developmental delay. Feeding problems, vomiting, faltering growth, and developmental delay are frequently seen. Subcutaneous fat may be excessive over the buttocks and suprapubic region. Two distinct clinical courses are observed: (1) a nonfatal neurologic course with faltering growth, strabismus, developmental delay, cerebellar hypoplasia, and hepatopathy in infancy followed by neuropathy and retinitis pigmentosa in the first or second decade; and (2) a more severe neurologic-multivisceral course with approximately 20% mortality in the first year of life. The late-infantile and childhood ataxia–intellectual disability stage, which begins between ages three and ten years, is characterized by hypotonia, ataxia, severely delayed language and motor development, inability to walk, and IQ of 40 to 70; other findings include seizures, stroke-like episodes or transient unilateral loss of function, coagulopathy, retinitis pigmentosa, joint contractures, and skeletal deformities. In the adult stable disability stage, intellectual ability is stable; peripheral neuropathy is variable, progressive retinitis pigmentosa and myopia are seen, thoracic and spinal deformities with osteoporosis worsen, and premature aging is observed; females may lack secondary sexual development and males may exhibit decreased testicular volume. Hypogonadotropic hypogonadism and coagulopathy may occur. The risk for deep venous thrombosis is increased.

An autoimmune disorder characterized by the association of primary biliary cirrhosis with limited cutaneous systemic sclerosis. Onset occurs between 30-65 years. Occurs sporadically, but rare familial cases with an unknown inheritance pattern have been observed. There is no cure and management is mainly supportive.

Chylomicron retention disease (CMRD), characterized by the inability to secrete chylomicrons from the enterocytes following the ingestion of fat, typically presents in infancy with failure to thrive, diarrhea, vomiting, abdominal distention, and malabsorption of fat. This leads to steatorrhea – the severity of which relates to the fat content of the diet – and in some cases, hepatomegaly. Organ systems outside of the gastrointestinal tract may also be affected (often due to malnutrition and deficiencies of fat-soluble vitamins), including neuromuscular abnormalities (typically in the first or second decade of life) secondary to vitamin E deficiency, poor bone mineralization and delayed bone maturation due to vitamin D deficiency, prolonged international normalized ratio (INR) due to vitamin K deficiency, mild ophthalmologic issues (e.g., micronystagmus, delayed dark adaptation, abnormal visual evoked potentials, and abnormal scotopic electroretinograms), and (in a small proportion of adults) cardiomyopathy with decreased ejection fraction. Affected individuals typically have marked hypocholesterolemia, low plasma apolipoprotein B levels, normal-to-low plasma triglyceride levels, and low serum concentrations of fat-soluble vitamins (A, D, E, and K). Endoscopy typically demonstrates a gelée blanche ("white hoar frosting") appearance of the duodenal mucosa.

Congenital defects of bile acid synthesis are autosomal recessive disorders characterized by neonatal onset of progressive liver disease with cholestatic jaundice and malabsorption of lipids and lipid-soluble vitamins from the gastrointestinal tract resulting from a primary failure to synthesize bile acids. Affected infants show failure to thrive and secondary coagulopathy. In most forms of the disorder, there is a favorable response to oral bile acid therapy (summary by Cheng et al., 2003). Genetic Heterogeneity of Congenital Defects in Bile Acid Synthesis There are several disorders that result from defects in bile acid synthesis. See CBAS2 (235555), caused by mutation in the delta(4)-3-oxosteroid 5-beta-reductase gene (AKR1D1; 604741) on chromosome 7q33; CBAS3 (613812), caused by mutation in the 7-alpha hydroxylase gene (CYP7B1; 603711) on chromosome 8q12; CBAS4 (214950), caused by mutation in the AMACR gene (604489) on chromosome 5p13; CBAS5 (616278), caused by mutation in the ABCD3 gene (170995) on chromosome 1p21; and CBAS6 (617308), caused by mutation in the ACOX2 gene (601641) on chromosome 3p14. See also progressive familial intrahepatic cholestasis (PFIC1; 211600), which has a similar phenotype.

Congenital bile acid synthesis defect type 2 is a disorder characterized by cholestasis, a condition that impairs the production and release of a digestive fluid called bile from liver cells. Bile is used during digestion to absorb fats and fat-soluble vitamins, such as vitamins A, D, E, and K. People with congenital bile acid synthesis defect type 2 cannot produce (synthesize) bile acids, which are a component of bile that stimulate bile flow and help it absorb fats and fat-soluble vitamins. As a result, an abnormal form of bile is produced.\n\nThe signs and symptoms of congenital bile acid synthesis defect type 2 often develop in infancy. Affected infants usually have a failure to gain weight and grow at the expected rate (failure to thrive) and yellowing of the skin and eyes (jaundice) due to impaired bile flow and a buildup of partially formed bile. Excess fat in the feces (steatorrhea) is another feature of congenital bile acid synthesis defect type 2. As the condition progresses, affected individuals can develop liver abnormalities including inflammation or chronic liver disease (cirrhosis). Some individuals with congenital bile acid synthesis defect type 2 cannot absorb certain fat-soluble vitamins, which can result in softening and weakening of the bones (rickets) or problems with blood clotting that lead to prolonged bleeding.\n\nIf left untreated, congenital bile acid synthesis defect type 2 typically leads to cirrhosis and death in childhood.

Celiac disease is a systemic autoimmune disease that can be associated with gastrointestinal findings (diarrhea, malabsorption, abdominal pain and distension, bloating, vomiting, and weight loss) and/or highly variable non-gastrointestinal findings (dermatitis herpetiformis, chronic fatigue, joint pain/inflammation, iron deficiency anemia, migraines, depression, attention-deficit disorder, epilepsy, osteoporosis/osteopenia, infertility and/or recurrent fetal loss, vitamin deficiencies, short stature, failure to thrive, delayed puberty, dental enamel defects, and autoimmune disorders). Classic celiac disease, characterized by mild to severe gastrointestinal symptoms, is less common than non-classic celiac disease, characterized by absence of gastrointestinal symptoms.

Congenital disorders of glycosylation (CDGs) are a genetically heterogeneous group of autosomal recessive disorders caused by enzymatic defects in the synthesis and processing of asparagine (N)-linked glycans or oligosaccharides on glycoproteins. Type I CDGs comprise defects in the assembly of the dolichol lipid-linked oligosaccharide (LLO) chain and its transfer to the nascent protein. These disorders can be identified by a characteristic abnormal isoelectric focusing profile of plasma transferrin (Leroy, 2006). For a discussion of the classification of CDGs, see CDG1A (212065). CDG Ib is clinically distinct from most other CDGs by the lack of significant central nervous system involvement. The predominant symptoms are chronic diarrhea with failure to thrive and protein-losing enteropathy with coagulopathy. Some patients develop hepatic fibrosis. CDG Ib is also different from other CDGs in that it can be treated effectively with oral mannose supplementation, but can be fatal if untreated (Marquardt and Denecke, 2003). Thus, CDG Ib should be considered in the differential diagnosis of patients with unexplained hypoglycemia, chronic diarrhea, liver disease, or coagulopathy in order to allow early diagnosis and effective therapy (Vuillaumier-Barrot et al., 2002) Freeze and Aebi (1999) reviewed CDG Ib and CDG Ic (603147). Marques-da-Silva et al. (2017) systematically reviewed the literature concerning liver involvement in CDG.

This syndrome is characterized by exocrine pancreatic insufficiency, dyserythropoietic anemia, and calvarial hyperostosis. It has been described in four children, three boys and one girl, from two consanguineous families. The disease is due to a mutation in the COX4I2 gene, encoding a mitochondrial cytochrome C oxidase sub-unit. Transmission is autosomal recessive.

Mitochondrial HMG-CoA synthase deficiency (HMGCS2D) is an inherited metabolic disorder caused by a defect in the enzyme that regulates the formation of ketone bodies. Patients present with hypoketotic hypoglycemia, encephalopathy, and hepatomegaly, usually precipitated by an intercurrent infection or prolonged fasting (summary by Aledo et al., 2006).

Congenital bile acid synthesis defect-3 (CBAS3) is an autosomal recessive disorder characterized by prolonged jaundice after birth, hepatomegaly, conjugated hyperbilirubinemia, elevations in characteristic abnormal bile acids, and progressive intrahepatic cholestasis with liver fibrosis (summary by Setchell et al., 1998 and Ueki et al., 2008). For a general phenotypic description and a discussion of genetic heterogeneity of congenital bile acid synthesis defects, see 607765.

Congenital pancreatic lipase deficiency is a rare, monoenzymatic form of exocrine pancreatic failure. All reported patients have presented with similar symptoms and clinical findings, including oily/greasy stools from infancy or early childhood and the absence of discernible pancreatic disease. Failure to thrive has not been observed. Analyses of duodenal contents consistently show a marked decrease of pancreatic lipolytic activity (summary by Figarella et al., 1980).

Zellweger spectrum disorder (ZSD) is a phenotypic continuum ranging from severe to mild. While individual phenotypes (e.g., Zellweger syndrome [ZS], neonatal adrenoleukodystrophy [NALD], and infantile Refsum disease [IRD]) were described in the past before the biochemical and molecular bases of this spectrum were fully determined, the term "ZSD" is now used to refer to all individuals with a defect in one of the ZSD-PEX genes regardless of phenotype. Individuals with ZSD usually come to clinical attention in the newborn period or later in childhood. Affected newborns are hypotonic and feed poorly. They have distinctive facies, congenital malformations (neuronal migration defects associated with neonatal-onset seizures, renal cysts, and bony stippling [chondrodysplasia punctata] of the patella[e] and the long bones), and liver disease that can be severe. Infants with severe ZSD are significantly impaired and typically die during the first year of life, usually having made no developmental progress. Individuals with intermediate/milder ZSD do not have congenital malformations, but rather progressive peroxisome dysfunction variably manifest as sensory loss (secondary to retinal dystrophy and sensorineural hearing loss), neurologic involvement (ataxia, polyneuropathy, and leukodystrophy), liver dysfunction, adrenal insufficiency, and renal oxalate stones. While hypotonia and developmental delays are typical, intellect can be normal. Some have osteopenia; almost all have ameleogenesis imperfecta in the secondary teeth.

Pancreatic agenesis-2 (PAGEN2) is an autosomal recessive disorder characterized by neonatal-onset diabetes mellitus and pancreatic exocrine deficiency (Weedon et al., 2014). For a discussion of genetic heterogeneity of pancreatic agenesis, see PAGEN1 (260370).

Infantile-onset multisystem neurologic, endocrine, and pancreatic disease-1 (IMNEPD1) is an autosomal recessive multisystemic disorder with variable expressivity. The core features usually include global developmental delay with impaired intellectual development and speech delay, ataxia, sensorineural hearing loss, and pancreatic insufficiency. Additional features may include peripheral neuropathy, postnatal microcephaly, dysmorphic facial features, and cerebellar atrophy. However, some patients may not display all features (summary by Picker-Minh et al., 2016, Sharkia et al., 2017). Genetic Heterogeneity of Infantile-Onset Multisystem Neurologic, Endocrine, and Pancreatic Disease See also IMNEPD2 (619418), caused by mutation in the YARS1 gene (603623) on chromosome 1p35.

Congenital bile acid synthesis defect-6 (CBAS6) is characterized by persistent hypertransaminasemia and accumulation of C27 bile acids (summary by Alonso-Pena et al., 2022). For a general phenotypic description and a discussion of genetic heterogeneity of congenital bile acid synthesis defects, see CBAS1 (607765).

Individuals with biallelic APOB-related familial hypobetalipoproteinemia (APOB-FHBL) may present from infancy through to adulthood with a range of clinical symptoms including deficiency of fat-soluble vitamins and gastrointestinal and neurologic dysfunction. Affected individuals typically have plasma total cholesterol, LDL cholesterol, and apo B levels below the fifth centile for age and sex. Acanthocytosis, elevated liver enzymes, and hyperbilirubinemia may also be found. The most common clinical findings are hepatomegaly, steatorrhea, and failure to thrive / growth deficiency. In the absence of treatment, affected individuals can develop atypical pigmentation of the retina; progressive loss of deep tendon reflexes, vibratory sense, and proprioception; muscle pain or weakness; dysarthria; ataxia; tremors; and steatohepatitis, fibrosis, and rarely, cirrhosis of the liver. Individuals with a heterozygous, typically truncating pathogenic variant in APOB are usually asymptomatic with mild liver dysfunction and hepatic steatosis. However, about 5%-10% of individuals with heterozygous APOB-FHBL develop relatively more severe nonalcoholic steatohepatitis requiring medical attention and occasionally progressing to cirrhosis, albeit very rarely.

Shwachman-Diamond syndrome (SDS) is characterized by: exocrine pancreatic dysfunction with malabsorption, malnutrition, and growth failure; hematologic abnormalities with single- or multilineage cytopenias and susceptibility to myelodysplasia syndrome (MDS) and acute myelogeneous leukemia (AML); and bone abnormalities. In almost all affected children, persistent or intermittent neutropenia is a common presenting finding, often before the diagnosis of SDS is made. Short stature and recurrent infections are common.

Shwachman-Diamond syndrome (SDS) is characterized by: exocrine pancreatic dysfunction with malabsorption, malnutrition, and growth failure; hematologic abnormalities with single- or multilineage cytopenias and susceptibility to myelodysplasia syndrome (MDS) and acute myelogeneous leukemia (AML); and bone abnormalities. In almost all affected children, persistent or intermittent neutropenia is a common presenting finding, often before the diagnosis of SDS is made. Short stature and recurrent infections are common.

Trichohepatoneurodevelopmental syndrome is a complex multisystem disorder characterized by woolly or coarse hair, liver dysfunction, pruritus, dysmorphic features, hypotonia, and severe global developmental delay (Morimoto et al., 2018).

Autosomal dominant severe congenital neutropenia-8 (SCN8) is a pleiotropic disorder with the consistent feature of decreased neutrophils associated with recurrent bacterial infections apparent from early infancy. Other hematologic parameters are usually normal, although some patients may have mild anemia. Bone marrow examination shows hypocellularity with arrested maturation of the granulocyte lineage at the level of promyelocytes or myeloblasts. Treatment with granulocyte colony-stimulating factor (GCSF; 138970) is usually ineffective or only partially effective, whereas hematopoietic bone marrow transplantation is effective. A subset of patients have additional features, including exocrine pancreatic insufficiency, which resembles Shwachman-Diamond syndrome (see SDS1, 260400), and/or neurologic deficits, including developmental delay, impaired intellectual development, speech delay, and/or autistic features (summary by Carapito et al., 2017 and Bellanne-Chantelot et al., 2018). For discussion of genetic heterogeneity of severe congenital neutropenia, see SCN1 (202700).

A rare intestinal disorder of neonates of unknown etiology. Patients are born with a short small bowel (less than 75 cm in length) that compromises proper intestinal absorption and leads chronic diarrhea, vomiting and failure to thrive.

Familial hypercholanemia-1 (FHCA1) is an autosomal recessive disorder characterized by elevated concentrations of bile acids (usually conjugated), itching, and fat malabsorption, leading to poor overall growth and deficiencies of fat-soluble vitamins. Vitamin D deficiency results in rickets, and vitamin K deficiency results in a coagulopathy (Morton et al., 2000; Shneider et al., 1997; summary by Carlton et al., 2003). See also bile acid conjugation defect-1 (BACD1; 619232), which can also show increased bile acid levels, although the bile acids in BACD1 are unconjugated. Genetic Heterogeneity of FHCA See FHCA2 (619256), caused by mutation in the SLC10A1 gene (182396) on chromosome 14q24.

Primary bile acid malabsorption (PBAM) is an intestinal disorder associated with chronic watery diarrhea, excess fecal bile acids, and steatorrhea. Bile acid malabsorption has been classified into 3 main types depending on the etiology. Types 1 and 3 are secondary disorders: type 1 is due to ileal dysfunction resulting from Crohn disease or ileal resection, and type 3 is secondary to other conditions, including cholecystectomy, post-vagotomy, celiac disease, and pancreatic insufficiency. Type 2 bile acid malabsorption is a primary congenital disorder, including the rare type due to mutations in the SLC10A2 gene (review by Pattni and Walters, 2009). Genetic Heterogeneity of Primary Bile Acid Malabsorption Also see PBAM2 (619481), caused by mutation in the SLC51B gene (612085).

Primary bile acid malabsorption-2 (PBAM2) is an autosomal recessive disorder characterized by chronic diarrhea, severe fat-soluble vitamin deficiency, and features of cholestatic liver disease (Sultan et al., 2018). For discussion of genetic heterogeneity of primary bile acid malabsorption, see PBAM1 (613291).