Ellis-van Creveld syndrome is an autosomal recessive skeletal dysplasia characterized by short limbs, short ribs, postaxial polydactyly, and dysplastic nails and teeth. Congenital cardiac defects, most commonly a defect of primary atrial septation producing a common atrium, occur in 60% of affected individuals (summary by Ruiz-Perez et al., 2000). The clinical features of the Ellis-van Creveld syndrome appear to be identical regardless of whether the disorder is caused by mutation in the EVC gene (604831) or in the EVC2 gene (607261) (Ruiz-Perez et al., 2003, Galdzicka et al., 2002).

Focal dermal hypoplasia is a multisystem disorder characterized primarily by involvement of the skin, skeletal system, eyes, and face. Skin manifestations present at birth include atrophic and hypoplastic areas of skin; cutis aplasia; fat nodules in the dermis manifesting as soft, yellow-pink cutaneous nodules; and pigmentary changes. Verrucoid papillomas of the skin and mucous membranes may appear later. The nails can be ridged, dysplastic, or hypoplastic; hair can be sparse or absent. Limb malformations include oligo-/syndactyly and split hand/foot. Developmental abnormalities of the eye can include anophthalmia/microphthalmia, iris and chorioretinal coloboma, and lacrimal duct abnormalities. Craniofacial findings can include facial asymmetry, notched alae nasi, cleft lip and palate, and pointed chin. Occasional findings include dental anomalies, abdominal wall defects, diaphragmatic hernia, and renal anomalies. Psychomotor development is usually normal; some individuals have cognitive impairment.

Incontinentia pigmenti (IP) is a disorder that affects the skin, hair, teeth, nails, eyes, and central nervous system; it occurs primarily in females and on occasion in males. Characteristic skin lesions evolve through four stages: I. Blistering (birth to age ~4 months). II. Wart-like rash (for several months). III. Swirling macular hyperpigmentation (age ~6 months into adulthood). IV. Linear hypopigmentation. Alopecia, hypodontia, abnormal tooth shape, and dystrophic nails are observed. Neovascularization of the retina, present in some individuals, predisposes to retinal detachment. Neurologic findings including seizures, intellectual disability, and developmental delays are occasionally seen.

Hypohidrotic ectodermal dysplasia (HED) is characterized by hypotrichosis (sparseness of scalp and body hair), hypohidrosis (reduced ability to sweat), and hypodontia (congenital absence of teeth). The cardinal features of classic HED become obvious during childhood. The scalp hair is thin, lightly pigmented, and slow growing. Sweating, although present, is greatly deficient, leading to episodes of hyperthermia until the affected individual or family acquires experience with environmental modifications to control temperature. Only a few abnormally formed teeth erupt, at a later-than-average age. Physical growth and psychomotor development are otherwise within normal limits. Mild HED is characterized by mild manifestations of any or all the characteristic features.

Aarskog-Scott syndrome is a genetic disorder that affects the development of many parts of the body, most commonly the head and face, the hands and feet, and the genitals and urinary system (genitourinary tract). This condition mainly affects males, although females may have mild features of the syndrome.\n\nPeople with Aarskog-Scott syndrome often have distinctive facial features, such as widely spaced eyes (hypertelorism), a small nose, a long area between the nose and mouth (philtrum), and a widow's peak hairline. They frequently have mild to moderate short stature during childhood, but their growth usually catches up with that of their peers during puberty. Hand abnormalities are common in this syndrome and include short fingers (brachydactyly), curved pinky fingers (fifth finger clinodactyly), webbing of the skin between some fingers (cutaneous syndactyly), and a single crease across the palm. Affected individuals can also have wide, flat feet with broad, rounded toes. Other abnormalities in people with Aarskog-Scott syndrome include heart defects and a split in the upper lip (cleft lip) with or without an opening in the roof of the mouth (cleft palate).\n\nMost males with Aarskog-Scott syndrome have a shawl scrotum, in which the scrotum surrounds the penis instead of hanging below. Less often, they have undescended testes (cryptorchidism) or a soft out-pouching around the belly-button (umbilical hernia) or in the lower abdomen (inguinal hernia).\n\nThe intellectual development of people with Aarskog-Scott syndrome varies widely. Most individuals with Aarskog-Scott syndrome have normal intelligence; however, some may have mild learning and behavior problems, and in rare cases, severe intellectual disability has been reported.

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.

The FLNB disorders include a spectrum of phenotypes ranging from mild to severe. At the mild end are spondylocarpotarsal synostosis (SCT) syndrome and Larsen syndrome; at the severe end are the phenotypic continuum of atelosteogenesis types I (AOI) and III (AOIII) and Piepkorn osteochondrodysplasia (POCD). SCT syndrome is characterized by postnatal disproportionate short stature, scoliosis and lordosis, clubfeet, hearing loss, dental enamel hypoplasia, carpal and tarsal synostosis, and vertebral fusions. Larsen syndrome is characterized by congenital dislocations of the hip, knee, and elbow; clubfeet (equinovarus or equinovalgus foot deformities); scoliosis and cervical kyphosis, which can be associated with a cervical myelopathy; short, broad, spatulate distal phalanges; distinctive craniofacies (prominent forehead, depressed nasal bridge, malar flattening, and widely spaced eyes); vertebral anomalies; and supernumerary carpal and tarsal bone ossification centers. Individuals with SCT syndrome and Larsen syndrome can have midline cleft palate and hearing loss. AOI and AOIII are characterized by severe short-limbed dwarfism; dislocated hips, knees, and elbows; and clubfeet. AOI is lethal in the perinatal period. In individuals with AOIII, survival beyond the neonatal period is possible with intensive and invasive respiratory support. Piepkorn osteochondrodysplasia (POCD) is a perinatal-lethal micromelic dwarfism characterized by flipper-like limbs (polysyndactyly with complete syndactyly of all fingers and toes, hypoplastic or absent first digits, and duplicated intermediate and distal phalanges), macrobrachycephaly, prominant forehead, hypertelorism, and exophthalmos. Occasional features include cleft palate, omphalocele, and cardiac and genitourinary anomalies. The radiographic features at mid-gestation are characteristic.

Pycnodysostosis is characterized by short-limbed short stature, typical facial appearance (convex nasal ridge and small jaw with obtuse mandibular angle), osteosclerosis with increased bone fragility, acroosteolysis of the distal phalanges, delayed closure of the cranial sutures, and dysplasia of the clavicle. In affected individuals, the facial features become more prominent with age, likely due to progressive acroosteolysis of the facial bones, but can usually be appreciated from early childhood, particularly the small jaw and convex nasal ridge. Additional features include dental and nail anomalies. Intelligence is typically normal with mild psychomotor difficulties reported in some individuals.

Coffin-Lowry syndrome (CLS) is usually characterized by severe-to-profound intellectual disability in males; less severely impaired individuals have been reported. Neuropsychiatric concerns can include behavioral problems, loss of strength, progressive spasticity or paraplegia, sleep apnea, or stroke. Stimulus-induced drop attacks (SIDAs) in which unexpected tactile or auditory stimuli or excitement triggers a brief collapse but no loss of consciousness are present in approximately 20% of affected individuals. Typically SIDAs begin between mid-childhood and the teens. Characteristic facial features may be more apparent with age. Upper-extremity differences may be subtle and include short, soft, fleshy hands with tapered fingers as well as fleshy forearms. Progressive kyphoscoliosis is one of the most difficult aspects of long-term care. Affected females tend to have intellectual disability in the mild-to-moderate range and may also have the typical facial, hand, and skeletal findings noted in males.

Junctional epidermolysis bullosa (JEB) is characterized by fragility of the skin and mucous membranes, manifest by blistering with little or no trauma. Blistering may be severe and granulation tissue can form on the skin around the oral and nasal cavities, fingers and toes, and internally around the upper airway. Blisters generally heal with no significant scarring. Broad classification of JEB includes JEB generalized severe and JEB generalized intermediate. In JEB generalized severe, blisters are present at birth or become apparent in the neonatal period. Congenital malformations of the urinary tract and bladder may also occur. In JEB generalized intermediate, the phenotype may be mild with blistering localized to hands, feet, knees, and elbows with or without renal or ureteral involvement. Some individuals never blister after the newborn period. Additional features shared by JEB and the other major forms of epidermolysis bullosa (EB) include congenital localized absence of skin (aplasia cutis congenita), milia, nail dystrophy, scarring alopecia, hypotrichosis, pseudosyndactyly, and other contractures.

Wiedemann-Rautenstrauch syndrome (WDRTS) is a rare autosomal recessive neonatal progeroid disorder characterized by intrauterine growth retardation, failure to thrive, short stature, a progeroid appearance, hypotonia, and variable mental impairment (summary by Toriello, 1990). Average survival in WDRTS is 7 months, although survival into the third decade of life has been reported (Akawi et al., 2013).

The TP63-related disorders comprise six overlapping phenotypes: Ankyloblepharon-ectodermal defects-cleft lip/palate (AEC) syndrome (which includes Rapp-Hodgkin syndrome). Acro-dermo-ungual-lacrimal-tooth (ADULT) syndrome. Ectrodactyly, ectodermal dysplasia, cleft lip/palate syndrome 3 (EEC3). Limb-mammary syndrome. Split-hand/foot malformation type 4 (SHFM4). Isolated cleft lip/cleft palate (orofacial cleft 8). Individuals typically have varying combinations of ectodermal dysplasia (hypohidrosis, nail dysplasia, sparse hair, tooth abnormalities), cleft lip/palate, split-hand/foot malformation/syndactyly, lacrimal duct obstruction, hypopigmentation, hypoplastic breasts and/or nipples, and hypospadias. Findings associated with a single phenotype include ankyloblepharon filiforme adnatum (tissue strands that completely or partially fuse the upper and lower eyelids), skin erosions especially on the scalp associated with areas of scarring, and alopecia, trismus, and excessive freckling.

A rare ectodermal dysplasia syndrome characterized by the association of sparse, fine, dry, slow growing hair with variable dental abnormalities including oligodontia, peg-shaped incisors, and shell teeth. Mild intellectual disability, microcephaly, and dysmorphic facial features have also been reported.

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.

Mulibrey nanism (MUL) is a rare autosomal recessive growth disorder with prenatal onset, including occasional progressive cardiomyopathy, characteristic facial features, failure of sexual maturation, insulin resistance with type 2 diabetes, and an increased risk for Wilms tumor (summary by Hamalainen et al., 2006).

Filippi syndrome is characterized by short stature, microcephaly, syndactyly, intellectual disability, and facial dysmorphism consisting of bulging forehead, broad and prominent nasal bridge, and diminished alar flare. Common features include cryptorchidism, speech impairment, and clinodactyly of the fifth finger, Some patients exhibit visual disturbances, polydactyly, seizures, and/or ectodermal abnormalities, such as nail hypoplasia, long eyelashes, hirsutism, and microdontia (summary by Hussain et al., 2014).

Odontoonychodermal dysplasia (OODD) is an autosomal recessive disorder characterized by dry hair, severe hypodontia, smooth tongue with marked reduction of fungiform and filiform papillae, onychodysplasia, hyperkeratosis of the palms and soles, hypo- and hyperhidrosis of the skin, and atrophic patches on the face (summary by Adaimy et al., 2007; Yu et al., 2019).

SHORT syndrome is a mnemonic for short stature, hyperextensibility, ocular depression (deeply set eyes), Rieger anomaly, and teething delay. It is now recognized that the features most consistently observed in SHORT syndrome are mild intrauterine growth restriction (IUGR); mild to moderate short stature; partial lipodystrophy (evident in the face, and later in the chest and upper extremities, often sparing the buttocks and legs); and a characteristic facial gestalt. Insulin resistance may be evident in mid-childhood or adolescence, although diabetes mellitus typically does not develop until early adulthood. Other frequent features include Axenfeld-Rieger anomaly or related ocular anterior chamber dysgenesis, delayed dentition and other dental issues, and sensorineural hearing loss.

Mulvihill-Smith syndrome is characterized by premature aging, multiple pigmented nevi, lack of facial subcutaneous fat, microcephaly, short stature, sensorineural hearing loss, and mental retardation. Immunodeficiency may also be a feature. Adult manifestations include the development of tumors, a sleep disorder with severe insomnia, and cognitive decline (summary by Yagihashi et al., 2009).

Barber-Say syndrome (BBRSAY) is a rare congenital condition characterized by severe hypertrichosis, especially of the back, skin abnormalities such as hyperlaxity and redundancy, and facial dysmorphism, including macrostomia, eyelid deformities, ocular telecanthus, abnormal and low-set ears, bulbous nasal tip with hypoplastic alae nasi, and low frontal hairline (summary by Roche et al., 2010).

The TP63-related disorders comprise six overlapping phenotypes: Ankyloblepharon-ectodermal defects-cleft lip/palate (AEC) syndrome (which includes Rapp-Hodgkin syndrome). Acro-dermo-ungual-lacrimal-tooth (ADULT) syndrome. Ectrodactyly, ectodermal dysplasia, cleft lip/palate syndrome 3 (EEC3). Limb-mammary syndrome. Split-hand/foot malformation type 4 (SHFM4). Isolated cleft lip/cleft palate (orofacial cleft 8). Individuals typically have varying combinations of ectodermal dysplasia (hypohidrosis, nail dysplasia, sparse hair, tooth abnormalities), cleft lip/palate, split-hand/foot malformation/syndactyly, lacrimal duct obstruction, hypopigmentation, hypoplastic breasts and/or nipples, and hypospadias. Findings associated with a single phenotype include ankyloblepharon filiforme adnatum (tissue strands that completely or partially fuse the upper and lower eyelids), skin erosions especially on the scalp associated with areas of scarring, and alopecia, trismus, and excessive freckling.

Axenfeld-Rieger syndrome is a disorder of morphogenesis that results in abnormal development of the anterior segment of the eye, which results in blindness from glaucoma in approximately 50% of affected individuals. Systemic abnormalities, including cardiac and dental anomalies, are associated. For a general phenotypic description and a discussion of genetic heterogeneity and nomenclature of Axenfeld-Rieger syndrome, see RIEG1 (180500).

A rare disorder with manifestation of hypo or oligodontia and acanthosis nigricans. It has been described in four generations of one family. Onset generally occurs during adolescence. Some patients are born with multiple teeth. Hair anomalies (sparse body and scalp hair) also reported. Inheritance is autosomal dominant.

Ichthyosis, leukocyte vacuoles, alopecia, and sclerosing cholangitis (ILVASC) is a rare autosomal recessive syndrome characterized by scalp hypotrichosis, scarring alopecia, ichthyosis, and sclerosing cholangitis (summary by Feldmeyer et al., 2006).

Van der Woude syndrome (VWS) is a dominantly inherited developmental disorder characterized by pits and/or sinuses of the lower lip, and cleft lip and/or cleft palate (CL/P, CP). It is the most common cleft syndrome. For a discussion of genetic heterogeneity of van der Woude syndrome, see VWS1 (119300).

Dermo-odonto dysplasia belongs to the group of tricho-odonto-onychial dysplasia. It has signs of variable severity: dry and thin skin, dental anomalies, nail alteration and trichodysplasia.

Primary failure of tooth eruption (PFE) is an autosomal dominant disorder in which nonankylosed posterior teeth fail to move along the eruption path cleared for them, resulting in a posterior open bite. Failure of affected teeth to respond to orthodontic force is a key characteristic (summary by Frazier-Bowers et al., 2007). See also 157950 and 273050 for phenotypes with shared features of PFE.

Wiedemann-Steiner syndrome (WSS) is characterized by developmental delay, intellectual disability, and characteristic facial features, with or without additional congenital anomalies. The facial features include thick eyebrows with lateral flare, vertically narrow and downslanted palpebral fissures, widely spaced eyes, long eyelashes, wide nasal bridge, broad nasal tip, thin vermilion of the upper lip, and thick scalp hair. About 60% of affected individuals have hypertrichosis cubiti ("hairy elbows"), which was once thought to be pathognomic for the syndrome, with a majority having hypertrichosis of other body parts. Other clinical features include feeding difficulties, prenatal and postnatal growth restriction, epilepsy, ophthalmologic anomalies, congenital heart defects, hand anomalies (such as brachydactyly and clinodactyly), hypotonia, vertebral anomalies (especially fusion anomalies of the cervical spine), renal and uterine anomalies, immune dysfunction, brain malformations, and dental anomalies.

Leukomelanoderma-infantilism-intellectual disability-hypodontia-hypotrichosis syndrome is a rare ectodermal dysplasia syndrome characterized by congenital generalized melanoleukoderma, hypodontia and hypotrichosis associated with infantilism, intellectual disability and growth delay. There have been no further descriptions in the literature since 1961.

Schopf-Schulz-Passarge syndrome (SSPS) is an autosomal recessive disorder characterized by a constellation of multiple eyelid cysts, hypodontia, hypotrichosis, palmoplantar hyperkeratosis, and onychodystrophy (summary by Mallaiah and Dickinson, 2001).

Cenani-Lenz syndactyly syndrome (CLSS) is an autosomal recessive disorder characterized mainly by anomalies of distal limb development, with fusion and disorganization of metacarpal and phalangeal bones, radius and ulnar shortening, radioulnar synostosis, and severe syndactyly of hands and feet. Mild facial dysmorphism is present in most patients. Kidney anomalies, including renal agenesis and hypoplasia, occur in over half of patients (summary by Li et al., 2010).

The TP63-related disorders comprise six overlapping phenotypes: Ankyloblepharon-ectodermal defects-cleft lip/palate (AEC) syndrome (which includes Rapp-Hodgkin syndrome). Acro-dermo-ungual-lacrimal-tooth (ADULT) syndrome. Ectrodactyly, ectodermal dysplasia, cleft lip/palate syndrome 3 (EEC3). Limb-mammary syndrome. Split-hand/foot malformation type 4 (SHFM4). Isolated cleft lip/cleft palate (orofacial cleft 8). Individuals typically have varying combinations of ectodermal dysplasia (hypohidrosis, nail dysplasia, sparse hair, tooth abnormalities), cleft lip/palate, split-hand/foot malformation/syndactyly, lacrimal duct obstruction, hypopigmentation, hypoplastic breasts and/or nipples, and hypospadias. Findings associated with a single phenotype include ankyloblepharon filiforme adnatum (tissue strands that completely or partially fuse the upper and lower eyelids), skin erosions especially on the scalp associated with areas of scarring, and alopecia, trismus, and excessive freckling.

The TP63-related disorders comprise six overlapping phenotypes: Ankyloblepharon-ectodermal defects-cleft lip/palate (AEC) syndrome (which includes Rapp-Hodgkin syndrome). Acro-dermo-ungual-lacrimal-tooth (ADULT) syndrome. Ectrodactyly, ectodermal dysplasia, cleft lip/palate syndrome 3 (EEC3). Limb-mammary syndrome. Split-hand/foot malformation type 4 (SHFM4). Isolated cleft lip/cleft palate (orofacial cleft 8). Individuals typically have varying combinations of ectodermal dysplasia (hypohidrosis, nail dysplasia, sparse hair, tooth abnormalities), cleft lip/palate, split-hand/foot malformation/syndactyly, lacrimal duct obstruction, hypopigmentation, hypoplastic breasts and/or nipples, and hypospadias. Findings associated with a single phenotype include ankyloblepharon filiforme adnatum (tissue strands that completely or partially fuse the upper and lower eyelids), skin erosions especially on the scalp associated with areas of scarring, and alopecia, trismus, and excessive freckling.

Ulnar-mammary syndrome (UMS) is an autosomal dominant disorder characterized by posterior limb deficiencies or duplications, apocrine/mammary gland hypoplasia and/or dysfunction, abnormal dentition, delayed puberty in males, and genital anomalies (Bamshad et al., 1996).

Orofaciodigital syndrome V (OFD5) is an autosomal recessive disorder characterized by cleft palate/uvula, lobulated tongue, frontal bossing, hypertelorism, postaxial polydactyly, and impaired intellectual development (summary by Faily et al., 2017).

Wolf-Hirschhorn syndrome is a congenital malformation syndrome characterized by pre- and postnatal growth deficiency, developmental disability of variable degree, characteristic craniofacial features ('Greek warrior helmet' appearance of the nose, high forehead, prominent glabella, hypertelorism, high-arched eyebrows, protruding eyes, epicanthal folds, short philtrum, distinct mouth with downturned corners, and micrognathia), and a seizure disorder (Battaglia et al., 2008).

A rare genetic developmental defect during embryogenesis disorder with characteristics of craniofacial dysmorphism (including brachycephaly, prominent forehead, sparse lateral eyebrows, severe hypertelorism, upslanting palpebral fissures, epicanthal folds, protruding ears, broad nasal bridge, pointed nasal tip, flat philtrum, anteverted nostrils, large mouth, thin upper vermilion border, highly arched palate and mild micrognathia) associated with osteopenia leading to repeated long bone fractures, severe myopia, mild to moderate sensorineural or mixed hearing loss, enamel hypoplasia, sloping shoulders and mild intellectual disability. There is evidence the disease can be caused by homozygous mutation in the IRX5 gene on chromosome 16q11.2.

Any tooth agenesis in which the cause of the disease is a mutation in the EDA gene.

Immunodeficiency-33 (IMD33) is an X-linked recessive disorder that affects only males. It is characterized by early-onset severe infections, usually due to pneumococcus, H. influenzae, and atypical mycobacteria, although other organisms have also been detected. Immunologic investigations may show variable abnormalities or may be normal. Disturbances include dysgammaglobulinemia with hypogammaglobulinemia, decreased IgG2, aberrant levels of IgM and IgA, and decreased class-switched memory B cells. There is often poor, but variable, response to vaccination; in particular, most patients do not develop antibodies to certain polysaccharide vaccines, notably pneumococcus. Other immunologic abnormalities may include impaired NK cytotoxic function, impaired cytokine production upon stimulation with IL1B (147720) or TNFA (191160), low IL6 (147620), low IL12 (see 161561), and decreased IFNG (147570). Patients do not have overt abnormalities of T-cell proliferation, although signaling pathways, such as CD40LG (300386)/CD40 (109535), may be disturbed. There is heterogeneity in the immunologic phenotype, resulting in highly variable clinical courses, most likely due to the different effects of hypomorphic mutations. Treatment with antibiotics and IVIg is usually beneficial; hematopoietic stem cell transplantation may not be necessary, but can be effective. Features of hypohidrotic ectodermal dysplasia are generally not present, although some patients may have conical teeth or hypodontia (summary by Orange et al., 2004, Filipe-Santos et al., 2006, Salt et al., 2008, Heller et al., 2020).

POLR3-related leukodystrophy, a hypomyelinating leukodystrophy with specific features on brain MRI, is characterized by varying combinations of four major clinical findings: Neurologic dysfunction, typically predominated by motor dysfunction (progressive cerebellar dysfunction, and to a lesser extent extrapyramidal [i.e., dystonia], pyramidal [i.e., spasticity] and cognitive dysfunctions). Abnormal dentition (delayed dentition, hypodontia, oligodontia, and abnormally placed or shaped teeth). Endocrine abnormalities such as short stature (in ~50% of individuals) with or without growth hormone deficiency, and more commonly, hypogonadotropic hypogonadism manifesting as delayed, arrested, or absent puberty. Ocular abnormality in the form of myopia, typically progressing over several years and becoming severe. POLR3-related leukodystrophy and 4H leukodystrophy are the two recognized terms for five previously described overlapping clinical phenotypes (initially described as distinct entities before their molecular basis was known). These include: Hypomyelination, hypodontia, hypogonadotropic hypogonadism (4H syndrome); Ataxia, delayed dentition, and hypomyelination (ADDH); Tremor-ataxia with central hypomyelination (TACH); Leukodystrophy with oligodontia (LO); Hypomyelination with cerebellar atrophy and hypoplasia of the corpus callosum (HCAHC). Age of onset is typically in early childhood but later-onset cases have also been reported. An infant with Wiedemann-Rautenstrauch syndrome (neonatal progeroid syndrome) was recently reported to have pathogenic variants in POLR3A on exome sequencing. Confirmation of this as a very severe form of POLR3-related leukodystrophy awaits replication in other individuals with a clinical diagnosis of Wiedemann-Rautenstrauch syndrome.

Ehlers-Danlos syndrome spondylodysplastic type 3 (EDSSPD3) is characterized by short stature, hyperelastic skin and hypermobile joints, protuberant eyes with bluish sclerae, finely wrinkled palms, and characteristic radiologic features (Giunta et al., 2008). For a discussion of genetic heterogeneity of the spondylodysplastic type of Ehlers-Danlos syndrome, see 130070.

EDAID2 is characterized by variable features of ectodermal dysplasia (e.g., hypo/anhidrosis, sparse hair, tooth anomalies) and various immunologic and infectious phenotypes of differing severity (summary by Boisson et al., 2017). Some patients may also have neutrophilia and autoinflammatory disease, such as liver disease (Tan et al., 2020). Mutations in the NFKBIA gene result in functional impairment of NFKB (see 164011), a master transcription factor required for normal activation of immune responses. Interruption of NFKB signaling results in decreased production of proinflammatory cytokines and certain interferons, rendering patients susceptible to infection (McDonald et al., 2007). For discussion of genetic heterogeneity of ectodermal dysplasia and immune deficiency, see 300291.

Alopecia, neurologic defects, and endocrinopathy syndrome (ANES) is an autosomal recessive disorder characterized by alopecia with skin involvement including multiple facial nevi and flexural hyperpigmentation; moderately to severely impaired intellectual development; progressive motor decline; and endocrine deficiency (summary by Spiegel et al., 2010).

Axenfeld-Rieger syndrome is primarily an eye disorder, although it can also affect other parts of the body. This condition is characterized by abnormalities of the front part of the eye, an area known as the anterior segment. For example, the colored part of the eye (the iris), may be thin or poorly developed. The iris normally has a single central hole, called the pupil, through which light enters the eye. People with Axenfeld-Rieger syndrome often have a pupil that is off-center (corectopia) or extra holes in the iris that can look like multiple pupils (polycoria). This condition can also cause abnormalities of the cornea, which is the clear front covering of the eye.\n\nAbout half of affected individuals develop glaucoma, a serious condition that increases pressure inside the eye. When glaucoma occurs with Axenfeld-Rieger syndrome, it most often develops in late childhood or adolescence, although it can occur as early as infancy. Glaucoma can cause vision loss or blindness.\n\nThe signs and symptoms of Axenfeld-Rieger syndrome can also affect other parts of the body. Many affected individuals have distinctive facial features such as widely spaced eyes (hypertelorism); a flattened mid-face with a broad, flat nasal bridge; and a prominent forehead. The condition is also associated with dental abnormalities including unusually small teeth (microdontia) or fewer than normal teeth (oligodontia). Some people with Axenfeld-Rieger syndrome have extra folds of skin around their belly button (redundant periumbilical skin). Other, less common features can include heart defects, the opening of the urethra on the underside of the penis (hypospadias), narrowing of the anus (anal stenosis), and abnormalities of the pituitary gland that can result in slow growth.\n\nResearchers have described at least three types of Axenfeld-Rieger syndrome. The types, which are numbered 1 through 3, are distinguished by their genetic cause.

Dermatosparaxis (meaning 'tearing of skin') is an autosomal recessive disorder of connective tissue resulting from deficiency of procollagen peptidase, an enzyme that aids in the processing of type I procollagen. The disorder and the responsible biochemical defect was first observed in cattle (Lapiere et al., 1971). Lapiere and Nusgens (1993) reviewed the discovery of dermatosparaxis in cattle, the elucidation of the disorder, its occurrence in other animals, and the delayed recognition of the disorder in the human.

Hypoglossia with situs inversus is a very rare congenital condition that likely represents a developmental field defect. Only sporadic cases have been reported (Faqeih et al., 2008). Hypoglossia is part of a group of malformation syndromes collectively termed 'oromandibular limb hypogenesis syndromes,' that usually include limb defects. Hall (1971) provided a classification system (see 103300). See also agnathia with holoprosencephaly (202650), which shows hypoglossia and situs inversus in addition to severe neurodevelopmental defects.

Malpositioning, or ectopic placement, of teeth is believed to result from a disturbance of the tooth developmental structure. Various forms of the disorder tend to be associated with one another and with hypodontia. It is important to recognize any associations of tooth anomalies as early diagnosis of developmental disturbance in a single tooth may reveal a potential risk of future position or eruption disturbances of other teeth and thus allow early intervention (Bjerklin et al., 1992).

Zlotogora-Ogur syndrome is an ectodermal dysplasia syndrome with characteristics of hair, skin and teeth anomalies, facial dysmorphism with cleft lip and palate, cutaneous syndactyly and, in some cases, intellectual disability.The prevalence is unknown but to date, less than 50 cases have been described in the literature. Caused by mutations in the gene PVRL1 (11q23-q24) which encodes nectin-1, the principal receptor used by alpha-herpesviruses to mediate entry into human cells. Transmission is autosomal recessive.

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.

Seckel syndrome is an autosomal recessive disorder characterized by proportionate short stature, severe microcephaly, mental retardation, and a typical 'bird-head' facial appearance (summary by Kalay et al., 2011). For a general phenotypic description and a discussion of genetic heterogeneity of Seckel syndrome, see 210600.

Kabuki syndrome (KS) is characterized by typical facial features (long palpebral fissures with eversion of the lateral third of the lower eyelid; arched and broad eyebrows; short columella with depressed nasal tip; large, prominent, or cupped ears), minor skeletal anomalies, persistence of fetal fingertip pads, mild-to-moderate intellectual disability, and postnatal growth deficiency. Other findings may include: congenital heart defects, genitourinary anomalies, cleft lip and/or palate, gastrointestinal anomalies including anal atresia, ptosis and strabismus, and widely spaced teeth and hypodontia. Functional differences can include: increased susceptibility to infections and autoimmune disorders, seizures, endocrinologic abnormalities (including isolated premature thelarche in females), feeding problems, and hearing loss.

Acrodysostosis-1 (ACRDYS1) is a form of skeletal dysplasia characterized by short stature, severe brachydactyly, facial dysostosis, and nasal hypoplasia. Affected individuals often have advanced bone age and obesity. Laboratory studies show resistance to multiple hormones, including parathyroid, thyrotropin, calcitonin, growth hormone-releasing hormone, and gonadotropin (summary by Linglart et al., 2011). However, not all patients show endocrine abnormalities (Lee et al., 2012). Genetic Heterogeneity of Acrodysostosis See also ACRDYS2 (614613), caused by mutation in the PDE4D gene (600129) on chromosome 5q12.

POLR3-related leukodystrophy, a hypomyelinating leukodystrophy with specific features on brain MRI, is characterized by varying combinations of four major clinical findings: Neurologic dysfunction, typically predominated by motor dysfunction (progressive cerebellar dysfunction, and to a lesser extent extrapyramidal [i.e., dystonia], pyramidal [i.e., spasticity] and cognitive dysfunctions). Abnormal dentition (delayed dentition, hypodontia, oligodontia, and abnormally placed or shaped teeth). Endocrine abnormalities such as short stature (in ~50% of individuals) with or without growth hormone deficiency, and more commonly, hypogonadotropic hypogonadism manifesting as delayed, arrested, or absent puberty. Ocular abnormality in the form of myopia, typically progressing over several years and becoming severe. POLR3-related leukodystrophy and 4H leukodystrophy are the two recognized terms for five previously described overlapping clinical phenotypes (initially described as distinct entities before their molecular basis was known). These include: Hypomyelination, hypodontia, hypogonadotropic hypogonadism (4H syndrome); Ataxia, delayed dentition, and hypomyelination (ADDH); Tremor-ataxia with central hypomyelination (TACH); Leukodystrophy with oligodontia (LO); Hypomyelination with cerebellar atrophy and hypoplasia of the corpus callosum (HCAHC). Age of onset is typically in early childhood but later-onset cases have also been reported. An infant with Wiedemann-Rautenstrauch syndrome (neonatal progeroid syndrome) was recently reported to have pathogenic variants in POLR3A on exome sequencing. Confirmation of this as a very severe form of POLR3-related leukodystrophy awaits replication in other individuals with a clinical diagnosis of Wiedemann-Rautenstrauch syndrome.

Any tooth agenesis in which the cause of the disease is a mutation in the MSX1 gene characterized by varying severity of tooth agenesis that may be seen in combination with orofacial clefting in some individuals.

Hypohidrotic ectodermal dysplasia (HED) is characterized by hypotrichosis (sparseness of scalp and body hair), hypohidrosis (reduced ability to sweat), and hypodontia (congenital absence of teeth). The cardinal features of classic HED become obvious during childhood. The scalp hair is thin, lightly pigmented, and slow growing. Sweating, although present, is greatly deficient, leading to episodes of hyperthermia until the affected individual or family acquires experience with environmental modifications to control temperature. Only a few abnormally formed teeth erupt, at a later-than-average age. Physical growth and psychomotor development are otherwise within normal limits. Mild HED is characterized by mild manifestations of any or all the characteristic features.

Axenfeld-Rieger syndrome is an autosomal dominant disorder of morphogenesis that results in abnormal development of the anterior segment of the eye, and results in blindness from glaucoma in approximately 50% of affected individuals (Fitch and Kaback, 1978). Systemic anomalies are associated, including dental hypoplasia, failure of involution of periumbilical skin, and maxillary hypoplasia (Alkemade, 1969). Genetic Heterogeneity of Axenfeld-Rieger Syndrome Linkage studies indicate that a second type of Axenfeld-Rieger syndrome maps to chromosome 13q14 (RIEG2; 601499). A third form of Axenfeld-Rieger syndrome (RIEG3; 602482) is caused by mutation in the FOXC1 gene (601090) on chromosome 6p25. See 109120 for a form of Axenfeld-Rieger syndrome associated with partially absent eye muscles, hydrocephalus, and skeletal abnormalities.

Hypohidrotic ectodermal dysplasia (HED) is characterized by hypotrichosis (sparseness of scalp and body hair), hypohidrosis (reduced ability to sweat), and hypodontia (congenital absence of teeth). The cardinal features of classic HED become obvious during childhood. The scalp hair is thin, lightly pigmented, and slow growing. Sweating, although present, is greatly deficient, leading to episodes of hyperthermia until the affected individual or family acquires experience with environmental modifications to control temperature. Only a few abnormally formed teeth erupt, at a later-than-average age. Physical growth and psychomotor development are otherwise within normal limits. Mild HED is characterized by mild manifestations of any or all the characteristic features.

Hypohidrotic ectodermal dysplasia (HED) is characterized by hypotrichosis (sparseness of scalp and body hair), hypohidrosis (reduced ability to sweat), and hypodontia (congenital absence of teeth). The cardinal features of classic HED become obvious during childhood. The scalp hair is thin, lightly pigmented, and slow growing. Sweating, although present, is greatly deficient, leading to episodes of hyperthermia until the affected individual or family acquires experience with environmental modifications to control temperature. Only a few abnormally formed teeth erupt, at a later-than-average age. Physical growth and psychomotor development are otherwise within normal limits. Mild HED is characterized by mild manifestations of any or all the characteristic features.

BBS5 is a ciliopathy associated with severe and early-onset retinal dystrophy, postaxial polydactyly, obesity, renal dysfunction, hypogonadism, and learning difficulties (summary by Scheidecker et al., 2015). Patients described by Young et al. (1999) and Moore et al. (2005) with mutations in the BBS5 gene did not have polydactyly. The contribution of BBS5 mutations to all cases of BBS has been estimated at 2% (Li et al., 2004) and 0.40% (Zaghloul and Katsanis, 2009). For a general phenotypic description and a discussion of genetic heterogeneity of Bardet-Biedl syndrome, see BBS1 (209900).

Desbuquois dysplasia, which belongs to the multiple dislocation group of disorders, is characterized by dislocations of large joints, severe pre- and postnatal growth retardation, joint laxity, and flat face with prominent eyes. Radiologic features include short long bones with an exaggerated trochanter that gives a 'monkey wrench' appearance to the proximal femur, and advanced carpal and tarsal ossification (summary by Bui et al., 2014). For a discussion of genetic heterogeneity of Desbuquois dysplasia, see DBQD1 (251450).

Developmental and epileptic encephalopathy-25 with amelogenesis imperfecta (DEE25) is an autosomal recessive neurologic disorder characterized by the onset of refractory seizures in early infancy. Most patients present with seizures in the neonatal period, which is often associated with status epilepticus. However, there is phenotypic variability, and some patients have onset of seizures later in infancy. Affected individuals show global developmental delay with intellectual disability and poor speech and communication. The seizures may remit somewhat with age, but there are persistent neurologic symptoms, including ataxia, spasticity, and abnormal involuntary movements. In addition to neurologic deficits, patients also have dental anomalies with amelogenesis imperfecta (summary by Thevenon et al., 2014 and Schossig et al., 2017). For a general phenotypic description and a discussion of genetic heterogeneity of DEE, see 308350.

A rare genetic ectodermal dysplasia syndrome characterized by short stature, nail dystrophy and/or nail loss, oral mucosa and/or tongue hyperpigmentation, dentition abnormalities (delayed teeth eruption, hypodontia, enamel hypoplasia), keratoderma on the margins of the palms and soles and focal hyperkeratosis on the dorsum of the hands and feet. Additionally, dysphagia with esophageal strictures, sensorineural deafness, bronchial asthma and severe iron-deficiency anemia have also been observed.

EVEN-plus syndrome (EVPLS) is characterized by prenatal-onset short stature, vertebral and epiphyseal changes, microtia, midface hypoplasia with flat nose and triangular nares, cardiac malformations, and other findings including anal atresia, hypodontia, and aplasia cutis. The features overlap those reported in patients with CODAS syndrome (600373; Royer-Bertrand et al., 2015).

The Cincinnati type of acrofacial dysostosis is a ribosomopathy characterized by a spectrum of mandibulofacial dysostosis phenotypes, with or without extrafacial skeletal defects (Weaver et al., 2015). In addition, a significant number of neurologic abnormalities have been reported, ranging from mild delays to refractory epilepsy, as well as an increased incidence of congenital heart defects, primarily septal in nature (Smallwood et al., 2023).

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). SRTD15 is characterized by narrow thorax, oral and cardiovascular anomalies, short long bones, and postaxial polydactyly, in addition to other congenital anomalies. Considerable variability in features and in severity has been reported, with some affected individuals succumbing shortly after birth and others living to adulthood, even within the same family. For a discussion of genetic heterogeneity of short-rib thoracic dysplasia with or without polydactyly, see SRTD1 (208500).

Bone marrow failure syndrome-3 is an autosomal recessive disorder characterized by onset of pancytopenia in early childhood. Patients may have additional variable nonspecific somatic abnormalities, including poor growth, microcephaly, and skin anomalies (summary by Tummala et al., 2016). BMFS3 has a distinct phenotype and may include features that overlap with Shwachman-Diamond syndrome (SDS1; 260400), such as pancreatic insufficiency and short stature, and with dyskeratosis congenita (see, e.g., DKCA1, 127550), such as dental and hair abnormalities and shortened telomeres. In addition, some patients may have joint and skeletal abnormalities, impaired development, and retinal dysplasia (summary by D'Amours et al., 2018). For a discussion of genetic heterogeneity of BMFS, see BMFS1 (614675).

Distal chromosome 19q13.11 deletion syndrome is an autosomal dominant neurodevelopmental disorder characterized by poor overall growth, slender habitus, microcephaly, delayed development, intellectual disability with poor or absent speech, and feeding difficulties. Additional features include dysmorphic facies, signs of ectodermal dysplasia, hand and foot anomalies, and genitourinary anomalies, particularly in males (summary by Chowdhury et al., 2014).

BBS21 is an autosomal recessive ciliopathy characterized by obesity, postaxial polydactyly, retinal degeneration, and mild cognitive impairment (Heon et al., 2016; Khan et al., 2016). For a general phenotypic description and a discussion of genetic heterogeneity of Bardet-Biedl syndrome, see BBS1 (209900).

Anauxetic dysplasia is a spondyloepimetaphyseal dysplasia characterized by severe short stature of prenatal onset, very short adult height (less than 1 meter), hypodontia, midface hypoplasia, and mild intellectual disability. Vertebrae are ovoid with concave dorsal surfaces in the lumbar region and show delayed bone maturation. Femoral heads and necks are hypoplastic, as are the iliac bodies. Long bones show irregular mineralization of the metaphyses. The first and fifth metacarpals are short and wide with small, late-ossifying epiphyses and bullet-shaped middle phalanges (summary by Barraza-Garcia et al., 2017). For a discussion of genetic heterogeneity of anauxetic dysplasia, see ANXD1 (607095).

NKX6-2-related disorder is characterized by a spectrum of progressive neurologic manifestations resulting from diffuse central nervous system hypomyelination. At the severe end of the spectrum is neonatal-onset nystagmus, severe spastic tetraplegia with joint contractures and scoliosis, and visual and hearing impairment, all of which rapidly progress resulting in death in early childhood. At the milder end of the spectrum is normal achievement of early motor milestones in the first year of life followed by slowly progressive complex spastic ataxia with pyramidal findings (spasticity with increased muscle tone and difficulty with gait and fine motor coordination) and cerebellar findings (nystagmus, extraocular movement disorder, dysarthria, titubation, and ataxia) with loss of developmental milestones. To date NKX6-2-related disorder has been reported in 25 individuals from 13 families.

Most commonly, IRF6-related disorders span a spectrum from isolated cleft lip and palate and Van der Woude syndrome (VWS) at the mild end to popliteal pterygium syndrome (PPS) at the more severe end. In rare instances, IRF6 pathogenic variants have also been reported in individuals with nonsyndromic orofacial cleft (18/3,811; 0.47%) and in individuals with spina bifida (2/192). Individuals with VWS show one or more of the following anomalies: Congenital, usually bilateral, paramedian lower-lip fistulae (pits) or sometimes small mounds with a sinus tract leading from a mucous gland of the lip. Cleft lip (CL). Cleft palate (CP). Note: Cleft lip with or without cleft palate (CL±P) is observed about twice as often as CP only. Submucous cleft palate (SMCP). The PPS phenotype includes the following: CL±P. Fistulae of the lower lip. Webbing of the skin extending from the ischial tuberosities to the heels. In males: bifid scrotum and cryptorchidism. In females: hypoplasia of the labia majora. Syndactyly of fingers and/or toes. Anomalies of the skin around the nails. A characteristic pyramidal fold of skin overlying the nail of the hallux (almost pathognomonic). In some nonclassic forms of PPS: filiform synechiae connecting the upper and lower jaws (syngnathia) or the upper and lower eyelids (ankyloblepharon). Other musculoskeletal anomalies may include spina bifida occulta, talipes equinovarus, digital reduction, bifid ribs, and short sternum. In VWS, PPS, IRF6-related neural tube defect, and IRF6-related orofacial cleft, growth and intelligence are typical.

The cartilage-hair hypoplasia – anauxetic dysplasia (CHH-AD) spectrum disorders are a continuum that includes the following phenotypes: Metaphyseal dysplasia without hypotrichosis (MDWH). Cartilage-hair hypoplasia (CHH). Anauxetic dysplasia (AD). CHH-AD spectrum disorders are characterized by severe disproportionate (short-limb) short stature that is usually recognized in the newborn, and occasionally prenatally because of the short extremities. Other findings include joint hypermobility, fine silky hair, immunodeficiency, anemia, increased risk for malignancy, gastrointestinal dysfunction, and impaired spermatogenesis. The most severe phenotype, AD, has the most pronounced skeletal phenotype, may be associated with atlantoaxial subluxation in the newborn, and may include cognitive deficiency. The clinical manifestations of the CHH-AD spectrum disorders are variable, even within the same family.

The blepharocheilodontic syndrome is a rare autosomal dominant disorder characterized by lower eyelid ectropion, upper eyelid distichiasis, euryblepharon, bilateral cleft lip and palate, and conical teeth. An additional rare manifestation is imperforate anus (summary by Weaver et al., 2010).

Any BAFopathy in which the cause of the disease is a mutation in the BCL11B gene.

Some ectodermal dysplasias are here classified as congenital disorders characterized by abnormal development in 2 or more ectodermal structures (hair, nails, teeth, and sweat glands) without other systemic findings. Ectodermal dysplasia-14 of the hair/tooth type (ECTD14) is primarily characterized by scalp hypotrichosis and hypodontia. Some patients have decreased sweating, and some show subtle facial dysmorphism (Peled et al., 2016). Rabie et al. (2022) tabulated the features of 24 patients with TSPEAR-associated ectodermal dysplasia, and found that of the various ectodermal derivatives, teeth were the most affected (82.6%), followed by hair (78.3%), nails (43.5%), and sweat glands (39.1%). The authors also noted that TSPEAR-associated dysmorphic facial features varied according to ethnic origin.

Myoectodermal gonadal dysgenesis syndrome (MEGD) is characterized by 46,XY complete or partial gonadal dysgenesis, or 46,XX gonadal dysgenesis, in association with extragonadal anomalies, including low birth weight, typical facies, rod and cone dystrophy, sensorineural hearing loss, omphalocele, anal atresia, renal agenesis, skeletal abnormalities, dry and scaly skin, severe myopathy, and neuromotor delay. Dysmorphic facial features along with muscular habitus are the hallmarks of the syndrome. Abnormal hair patterning with frontal upsweep and additional whorls, eyebrow abnormalities comprising broad, arched, and sparse or thick eyebrows, underdeveloped alae nasi, smooth philtrum, and low-set ears with overfolded helices facilitate a gestalt diagnosis. (Guran et al., 2019; Altunoglu et al., 2022).

Neurodevelopmental disorder with or without variable brain abnormalities (NEDBA) is characterized by global developmental delay apparent from infancy or early childhood, resulting in mildly delayed walking, variably impaired intellectual development, and poor or absent speech. Additional features may include hypotonia, spasticity, or ataxia. About half of patients have abnormal findings on brain imaging, including cerebral or cerebellar atrophy, loss of white matter volume, thin corpus callosum, and perisylvian polymicrogyria. Seizures are not a prominent finding, and although some patients may have nonspecific dysmorphic facial features, there is no common or consistent gestalt (summary by Platzer et al., 2019).

Lissencephaly-10 (LIS10) is a neurologic disorder characterized by variably delayed development with mildly to moderately impaired intellectual development and language delay, as well as seizures, which are often intractable. There is a spectrum of severity, with some patients having normal early development and only borderline to mild cognitive impairment. Brain imaging shows features consistent with neuronal migration defects, including posterior-predominant lissencephaly, pachygyria, agyria, and subcortical band heterotopia (summary by Tsai et al., 2020). For a general description and a discussion of genetic heterogeneity of lissencephaly, see LIS1 (607432).

Mandibuloacral dysplasia progeroid syndrome (MDPS) is an autosomal recessive severe laminopathy-like disorder characterized by growth retardation, bone resorption, arterial calcification, renal glomerulosclerosis, and hypertension (Elouej et al., 2020).

Cardioacrofacial dysplasia-2 (CAFD2) is characterized by congenital cardiac defects, primarily common atrium or atrioventricular septal defect; limb anomalies, including short limbs, brachydactyly, and postaxial polydactyly; and dysmorphic facial features. Developmental delay of variable severity has also been observed (Palencia-Campos et al., 2020). For a discussion of genetic heterogeneity of CAFD, see CAFD1 (619142).

X-linked multiple congenital anomalies-neurodevelopmental syndrome (MCAND) is an X-linked recessive congenital multisystemic disorder characterized by poor growth, global developmental delay with impaired intellectual development, and variable abnormalities of the cardiac, skeletal, and genitourinary systems. Most affected individuals also have hypotonia and dysmorphic craniofacial features. Brain imaging typically shows enlarged ventricles and thin corpus callosum; some have microcephaly, whereas others have hydrocephalus. The severity of the disorder is highly variable, ranging from death in early infancy to survival into the second or third decade. Pathogenetically, the disorder results from disrupted gene expression and signaling during embryogenesis, thus affecting multiple systems (summary by Tripolszki et al., 2021 and Beck et al., 2021). Beck et al. (2021) referred to the disorder as LINKED syndrome (LINKage-specific deubiquitylation deficiency-induced Embryonic Defects).

Short stature, facial dysmorphism, and skeletal anomalies with or without cardiac anomalies-2 (SSFSC2) is characterized by thin and short long bones, distinctive facial dysmorphism, and dental and skeletal abnormalities, in the absence of developmental delay or intellectual disability. Cardiac anomalies have been reported in some patients (Lin et al., 2021). For a discussion of genetic heterogeneity of SSFSC, see SSFSC1 (617877).

Alzahrani-Kuwahara syndrome (ALKUS) is an autosomal recessive neurodevelopmental syndrome characterized by global developmental delay with severely impaired intellectual function and poor or absent speech. Patients have poor overall growth and dysmorphic facial features. More variable findings include early-onset cataracts, hypotonia, congenital heart defects, lower limb spasticity, and hypospadias (summary by Alzahrani et al., 2020).

Hypomyelinating leukodystrophy-21 (HLD21) is an autosomal recessive neurodegenerative disorder characterized by global developmental delay apparent from infancy with loss of motor, speech, and cognitive milestones in the first decades of life. Affected individuals show cerebellar and pyramidal signs, including nystagmus, ataxia, dystonia, and spasticity, resulting in the loss of ambulation. Other more variable features include feeding difficulties, poor overall growth with microcephaly, optic atrophy, and seizures. Brain imaging shows diffuse hypomyelination of the white matter and atrophy of the cerebellum and corpus callosum. The disorder is progressive and may lead to premature death (summary by Dorboz et al., 2018). For a general phenotypic description and a discussion of genetic heterogeneity of HLD, see 312080.

Marbach-Rustad progeroid syndrome (MARUPS) is characterized by progeroid appearance with little subcutaneous fat and triangular facies, growth retardation with short stature, hypoplastic mandible crowded with unerupted supernumerary teeth, and cerebellar intention tremor. Psychomotor development is normal. Although features are reminiscent of Hutchinson-Gilford progeria syndrome (HGPS; 176670), MARUPS is less severe, with a relatively good prognosis. Two patients have been reported (Marbach et al., 2019).

Orofaciodigital syndrome XIX (OFD19) is an autosomal recessive ciliopathy characterized by tongue nodules; dental anomalies including congenital absence or abnormal shape of incisors; narrow, high-arched or cleft palate; retrognathia; and digital anomalies. Some patients have notching of the upper or lower lip (Iturrate et al., 2022).

Lacrimoauriculodentodigital syndrome-2 (LADD2) is a multiple congenital anomaly disorder mainly affecting lacrimal glands and ducts, salivary glands and ducts, ears, teeth, and distal limb segments (summary by Rohmann et al., 2006).

Lacrimoauriculodentodigital syndrome-1 (LADD1) is a multiple congenital anomaly disorder mainly affecting lacrimal glands and ducts, salivary glands and ducts, ears, teeth, and distal limb segments (summary by Rohmann et al., 2006). Genetic Heterogeneity of Lacrimoauriculodentodigital Syndrome LADD syndrome-2 (LADD2; 620192) is caused by mutation in the FGFR3 gene (134934) on chromosome 4p16, and LADD syndrome-3 (LADD3; 620193) is caused by mutation in the FGF10 gene, an FGFR ligand, on chromosome 5p12.

Neurodevelopmental disorder with seizures, spasticity, and partial or complete agenesis of the corpus callosum (NEDSSCC) is an autosomal recessive disorder characterized by axial hypotonia and global developmental delay apparent from the first days or months of life. Affected individuals often have feeding difficulties and develop early-onset seizures that tend to be well-controlled. Other features include peripheral spasticity with hyperreflexia, variable dysmorphic features, impaired intellectual development, behavioral abnormalities, and hypoplasia or absence of the corpus callosum on brain imaging (Faqeih et al., 2023).

Neurodevelopmental disorder with absent speech and movement and behavioral abnormalities (NEDSMB) is an autosomal recessive disorder characterized by global developmental delay and severely impaired intellectual development with aggressive behavior. Mild dysmorphic features and hypodontia are also present (Faqeih et al., 2023).