Bloom syndrome (BSyn) is characterized by severe pre- and postnatal growth deficiency, immune abnormalities, sensitivity to sunlight, insulin resistance, and a high risk for many cancers that occur at an early age. Despite their very small head circumference, most affected individuals have normal intellectual ability. Women may be fertile but often have early menopause, and men tend to be infertile, with only one confirmed case of paternity. Serious medical complications that are more common than in the general population and that also appear at unusually early ages include chronic obstructive pulmonary disease, diabetes mellitus as a result of insulin resistance, and cancer of a wide variety of types and anatomic sites.

Trichorhinophalangeal syndrome (TRPS) comprises TRPS I (caused by a heterozygous pathogenic variant in TRPS1) and TRPS II (caused by contiguous gene deletion of TRPS1, RAD21, and EXT1). Both types of TRPS are characterized by distinctive facial features; ectodermal features (fine, sparse, depigmented, and slow growing hair; dystrophic nails; and small breasts); and skeletal findings (short stature; short feet; brachydactyly with ulnar or radial deviation of the fingers; and early, marked hip dysplasia). TRPS II is characterized by multiple osteochondromas (typically first observed clinically on the scapulae and around the elbows and knees between ages 1 month and 6 years) and an increased risk of mild-to-moderate intellectual disability.

An autosomal recessive subtype of cerebrooculofacioskeletal syndrome caused by mutation(s) in the ERCC6 gene, encoding DNA excision repair protein ERCC-6.

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.

Microcephalic osteodysplastic primordial dwarfism type II (MOPDII), the most common form of microcephalic primordial dwarfism, is characterized by extreme short stature and microcephaly along with distinctive facial features. Associated features that differentiate it from other forms of primordial dwarfism and that may necessitate treatment include: abnormal dentition, a slender bone skeletal dysplasia with hip deformity and/or scoliosis, insulin resistance / diabetes mellitus, chronic kidney disease, cardiac malformations, and global vascular disease. The latter includes neurovascular disease such as moyamoya vasculopathy and intracranial aneurysms (which can lead to strokes), coronary artery disease (which can lead to premature myocardial infarctions), and renal vascular disease. Hypertension, which is also common, can have multiple underlying causes given the complex comorbidities.

Monosomy 18q is a partial deletion of the long arm of chromosome 18 characterized by highly variable phenotype, most commonly including hypotonia, developmental delay, short stature, growth hormone deficiency, hearing loss and external ear anomalies, intellectual disability, palatal defects, dysmorphic facial features, skeletal anomalies (foot deformities, tapering fingers, scoliosis) and mood disorders.

Floating-Harbor syndrome (FHS) is characterized by typical craniofacial features; low birth weight, normal head circumference, and short stature; bone age delay that normalizes between ages six and 12 years; skeletal anomalies (brachydactyly, clubbing, clinodactyly, short thumbs, prominent joints, clavicular abnormalities); severe receptive and expressive language impairment; hypernasality and high-pitched voice; and intellectual disability that is typically mild to moderate. Difficulties with temperament and behavior that are present in many children tend to improve in adulthood. Other features can include hyperopia and/or strabismus, conductive hearing loss, seizures, gastroesophageal reflux, renal anomalies (e.g., hydronephrosis / renal pelviectasis, cysts, and/or agenesis), and genital anomalies (e.g., hypospadias and/or undescended testes).

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).

A form of ectodermal dysplasia syndrome characterized by a short stature of prenatal onset, alopecia, ichthyosis, photophobia, ectrodactyly, seizures, scoliosis, multiple contractures, fusions of various bones (particularly elbows, carpals, metacarpals, and spine), intellectual disability, and facial dysmorphism (microdolichocephaly, madarosis, large ears and long nose). ACD syndrome overlaps with ichthyosis follicularis-alopecia-photophobia syndrome.

Lowry-Wood syndrome (LWS) is characterized by multiple epiphyseal dysplasia and microcephaly. Patients exhibit intrauterine growth retardation and short stature, as well as developmental delay and intellectual disability. Retinal degeneration has been reported in some patients (Farach et al., 2018; Shelihan et al., 2018). Microcephalic osteodysplastic primordial dwarfism type I (MOPD1; 210710) and Roifman syndrome (RFMN; 616651), the features of which overlap with those of Lowry-Wood syndrome, are also caused by biallelic mutation in the RNU4ATAC gene.

Jawad syndrome (JWDS) is an autosomal recessive disorder characterized by congenital microcephaly, moderate to severely impaired intellectual development, and digital malformations including phalangeal joint swelling, clinodactyly, polydactyly, syndactyly, and total absence of nails (summary by Qvist et al., 2011).

Nance-Horan syndrome (NHS) is an X-linked disorder characterized by congenital cataracts, dental anomalies, dysmorphic features, and, in some cases, mental retardation (summary by Burdon et al., 2003).

X-linked Dandy-Walker malformation with intellectual disability, basal ganglia disease and seizures (XDIBS), or Pettigrew syndrome is a central nervous system malformation characterized by severe intellectual deficit, early hypotonia with progression to spasticity and contractures, choreoathetosis, seizures, dysmorphic face (long face with prominent forehead), and brain imaging abnormalities such as Dandy-Walker malformation, and iron deposition. (From Mondo:0010574)

Traboulsi syndrome is characterized by dislocated crystalline lenses and anterior segment abnormalities in association with a distinctive facies involving flat cheeks and a beaked nose. Some affected individuals develop highly unusual nontraumatic conjunctival cysts (filtering blebs), presumably caused by abnormal thinning of the sclera (Patel et al., 2014).

Schilbach-Rott syndrome (SBRS) is an autosomal dominant disorder characterized by hypotelorism, epicanthal folds, cleft palate, dysmorphic facies, and hypospadias in males. The phenotype is variable; mild mental retardation has been reported (summary by Shkalim et al., 2009).

Prieto syndrome (PRS) is an X-linked intellectual developmental disorder characterized by mildly to severely impaired intellectual development, developmental delay, autism spectrum disorder, or neuropsychiatric symptoms, variably accompanied by speech delay, epilepsy, microcephaly, structural brain defects, and minor facial anomalies (summary by Kury et al., 2022).

X-linked intellectual deficit-cerebellar hypoplasia, also known as OPHN1 syndrome, is a rare syndromic form of cerebellar dysgenesis characterized by moderate to severe intellectual deficit and cerebellar abnormalities.

Uruguay faciocardiomusculoskeletal syndrome (FCMSU) is an X-linked disorder in which affected males have a distinctive facial appearance, muscular hypertrophy, and cardiac ventricular hypertrophy leading to premature death. Additional features include large, broad, and deformed hands and feet, congenital hip dislocation, and scoliosis (summary by Xue et al., 2016).

Seckel syndrome is a rare autosomal recessive disorder characterized by growth retardation, microcephaly with mental retardation, and a characteristic facial appearance (Borglum et al., 2001). For a general phenotypic description and a discussion of genetic heterogeneity of Seckel syndrome, see SCKL1 (210600).

LIG4 syndrome is an autosomal recessive severe combined immunodeficiency with features of radiosensitivity, chromosomal instability, pancytopenia, and developmental and growth delay. Leukemia and dysmorphic facial features have been reported in some patients (summary by van der Burg et al., 2006).

Patients with Richieri-Costa-Pereira syndrome display a pattern of anomalies consisting of microstomia, micrognathia, abnormal fusion of the mandible, cleft palate/Robin sequence, absence of lower central incisors, minor ear anomalies, hypoplastic first ray, abnormal tibiae, hypoplastic halluces, and clubfeet. Learning disability is also a common finding (summary by Favaro et al., 2011).

Radioulnar synostosis-developmental delay-hypotonia syndrome, also known as Der Kaloustian-McIntosh-Silver syndrome, is an extremely rare syndrome with synostosis described in about 4 patients to date with clinical manifestations including congenital unilateral radioulnar synostosis, generalized hypotonia, developmental delay, and dysmorphic facial features (long face, prominent nose and ears).

Keipert syndrome (KPTS) is characterized by craniofacial and digital abnormalities and variable learning difficulties. The distinctive facial appearance includes broad forehead, hypertelorism, prominent nose, wide mouth, and prominent upper lip with cupid bow configuration. Digital anomalies are also distinctive, with widening of all distal phalanges, particularly of the thumbs and great toes (Amor et al., 2019).

Any COFS syndrome in which the cause of the disease is a mutation in the ERCC2 gene.

Congenital deafness with labyrinthine aplasia, microtia, and microdontia (LAMM syndrome) is characterized by: profound bilateral congenital sensorineural deafness associated with inner ear anomalies (most often bilateral complete labyrinthine aplasia); microtia (type I) that is typically bilateral (although unilateral microtia and normal external ears are observed on occasion); and microdontia (small teeth). Individuals with LAMM syndrome commonly have motor delays during infancy presumably due to impaired balance from inner ear (vestibular) abnormalities. Growth, physical development, and cognition are normal.

KAT6B disorders include genitopatellar syndrome (GPS) and Say-Barber-Biesecker-Young-Simpson variant of Ohdo syndrome (SBBYSS) which are part of a broad phenotypic spectrum with variable expressivity; individuals presenting with a phenotype intermediate between GPS and SBBYSS have been reported. Both phenotypes are characterized by some degree of global developmental delay / intellectual disability; hypotonia; genital abnormalities; and skeletal abnormalities including patellar hypoplasia/agenesis, flexion contractures of the knees and/or hips, and anomalies of the digits, spine, and/or ribs. Congenital heart defects, small bowel malrotation, feeding difficulties, slow growth, cleft palate, hearing loss, and dental anomalies have been observed in individuals with either phenotype.

Hall-Riggs syndrome is a very rare syndrome consisting of microcephaly with facial dysmorphism, spondylometaepiphyseal dysplasia and severe intellectual deficit.

This syndrome is characterized by the association of a progressive leukodystrophy marked by generalized mental and motor impairment with the presence of thickened and wrinkled skin. It has been described in a Japanese brother and sister born to healthy parents. Both patients died in early childhood.

MCPH causes intellectual disability, which is typically mild to moderate and does not become more severe with age. Most affected individuals have delayed speech and language skills. Motor skills, such as sitting, standing, and walking, may also be mildly delayed.\n\nPeople with MCPH usually have few or no other features associated with the condition. Some have a narrow, sloping forehead; mild seizures; problems with attention or behavior; or short stature compared to others in their family. The condition typically does not affect any other major organ systems or cause other health problems.\n\nInfants with MCPH have an unusually small head circumference compared to other infants of the same sex and age. Head circumference is the distance around the widest part of the head, measured by placing a measuring tape above the eyebrows and ears and around the back of the head. Affected infants' brain volume is also smaller than usual, although they usually do not have any major abnormalities in the structure of the brain. The head and brain grow throughout childhood and adolescence, but they continue to be much smaller than normal.\n\nAutosomal recessive primary microcephaly (often shortened to MCPH, which stands for "microcephaly primary hereditary") is a condition in which infants are born with a very small head and a small brain. The term "microcephaly" comes from the Greek words for "small head."

Bowen-Conradi syndrome (BWCNS) is an autosomal recessive disorder characterized by severely impaired prenatal and postnatal growth, microcephaly, prominent nose with absent glabellar angle, micrognathia, joint abnormalities including flexion contractures, camptodactyly, rocker-bottom feet, and severe psychomotor delay. Most patients do not survive beyond the first year of life as a result of complications associated with reduced mobility and failure to thrive (summary by Armistead et al., 2009).

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).

A multiple malformation syndrome in which mandibulofacial dysostosis and severe limb reduction defects are associated with complex malformations of different organs and systems especially the central nervous system, urogenital tract, heart, and lungs. The mandibulofacial defect causes death by respiratory distress. Limb reduction is severe and includes shoulder and pelvis hypoplasia, phocomelia with humerus hypoplasia, absent radius and ulna, complete absence of long bones of the legs, and various hand anomalies, predominantly preaxial reduction. These infants also show facial dysmorphism and ear anomalies. The condition is a rare with an autosomal recessive mode of inheritance. The prognosis is poor and this condition leads to death in utero or shortly after birth.

Stormorken syndrome is an autosomal dominant disorder characterized by mild bleeding tendency due to platelet dysfunction, thrombocytopenia, anemia, asplenia, tubular aggregate myopathy, congenital miosis, and ichthyosis. Additional features may include headache or recurrent stroke-like episodes (summary by Misceo et al., 2014).

Familial anonychia/onychodystrophy with hypoplasia or absence of distal phalanges (ODP) is a rare disorder characterized by onychodystrophy, anonychia, brachydactyly of the fifth finger, and digitalization of the thumbs, with absence or hypoplasia of the distal phalanges of the hands and feet. Generally the nails of the first to third digits are progressively deformed with total anonychia in the last 2 digits and in all toes (summary by Genzer-Nir et al., 2010). A syndrome has been described in which affected females display juvenile hypertrophy of the breast (JHB; 113670) in association with ODP, whereas males have only ODP (mammary-digital-nail syndrome; 613689).

Chromosome 16p13.3deletion syndrome is a chromosome abnormality that can affect many parts of the body. People with this condition are missing a small piece (deletion) of chromosome 16 at a location designated p13.3. Although once thought to be a severe form of Rubinstein-Taybi syndrome, it is now emerging as a unique syndrome. Signs and symptoms may include failure to thrive, hypotonia (reduced muscle tone), short stature, microcephaly (unusually small head), characteristic facial features, mild to moderate intellectual disability, organ anomalies (i.e. heart and/or kidney problems), and vulnerability to infections. Chromosome testing of both parents can provide information about whether the deletion was inherited. In most cases, parents do not have any chromosome abnormalities. However, sometimes one parent has a balanced translocation where a piece of a chromosome has broken off and attached to another one with no gain or loss of genetic material. The balanced translocation normally does not cause signs or symptoms, but it increases the risk for having a child with a chromosome abnormality like a deletion. Treatment is based on the signs and symptoms present in each person.To learn more about chromosome abnormalities in general, view our GARD fact sheet on Chromosome Disorders.

MBD5 haploinsufficiency is a neurodevelopmental disorder characterized by developmental delay, intellectual disability, severe speech impairment, seizures, sleep disturbances, and abnormal behaviors. Most children lack speech entirely or have single words, short phrases, or short sentences. Seizures are present in more than 80% of children; onset is usually around age two years. Sleep disturbances, present in about 90%, can result in excessive daytime drowsiness. Abnormal behaviors can include autistic-like behaviors (80%) and self-injury and aggression (>60%).

Any autosomal recessive non-syndromic intellectual disability in which the cause of the disease is a mutation in the NSUN2 gene.

10q26 deletion syndrome is a condition that results from the loss (deletion) of a small piece of chromosome 10 in each cell. The deletion occurs on the long (q) arm of the chromosome at a position designated 10q26.\n\nThe signs and symptoms of 10q26 deletion syndrome vary widely, even among affected members of the same family. Among the more common features associated with this chromosomal change are distinctive facial features, mild to moderate intellectual disability, growth problems, and developmental delay. People with 10q26 deletion syndrome often have delayed development of speech and of motor skills such as sitting, crawling, and walking. Some have limited speech throughout life. Affected individuals may experience seizures, attention-deficit/hyperactivity disorder (ADHD), poor impulse control (impulsivity), or exhibit autistic behaviors that affect communication and social interaction.\n\nA range of facial features is seen in people with 10q26 deletion syndrome, but not all affected individuals have these features. Facial features of people with 10q26 deletion syndrome may include a prominent or beaked nose, a broad nasal bridge, a small jaw (micrognathia), malformed ears that are low set, a thin upper lip, and an unusually small head size (microcephaly). Many affected individuals have widely spaced eyes (hypertelorism) that do not look in the same direction (strabismus). Some people with this condition have a short neck with extra folds of skin (webbed neck).\n\nLess common signs and symptoms can occur in 10q26 deletion syndrome. Skeletal problems include a spine that curves to the side (scoliosis), limited movement in the elbows or other joints, or curved fifth fingers and toes (clinodactyly). Slow growth before and after birth can also occur in affected individuals. Males with this condition may have genital abnormalities, such as a small penis (micropenis), undescended testes (cryptorchidism), or the urethra opening on the underside of the penis (hypospadias). Some people with 10q26 deletion syndrome have kidney abnormalities, heart defects, breathing problems, recurrent infections, or hearing or vision problems.

Autosomal recessive primary microcephaly (often shortened to MCPH, which stands for "microcephaly primary hereditary") is a condition in which infants are born with a very small head and a small brain. The term "microcephaly" comes from the Greek words for "small head."\n\nInfants with MCPH have an unusually small head circumference compared to other infants of the same sex and age. Head circumference is the distance around the widest part of the head, measured by placing a measuring tape above the eyebrows and ears and around the back of the head. Affected infants' brain volume is also smaller than usual, although they usually do not have any major abnormalities in the structure of the brain. The head and brain grow throughout childhood and adolescence, but they continue to be much smaller than normal.\n\nPeople with MCPH usually have few or no other features associated with the condition. Some have a narrow, sloping forehead; mild seizures; problems with attention or behavior; or short stature compared to others in their family. The condition typically does not affect any other major organ systems or cause other health problems.\n\nMCPH causes intellectual disability, which is typically mild to moderate and does not become more severe with age. Most affected individuals have delayed speech and language skills. Motor skills, such as sitting, standing, and walking, may also be mildly delayed.

The 1q21.1 recurrent microdeletion itself does not appear to lead to a clinically recognizable syndrome as some persons with the deletion have no obvious clinical findings and others have variable findings that most commonly include microcephaly (50%), mild intellectual disability (30%), mildly dysmorphic facial features, and eye abnormalities (26%). Other findings can include cardiac defects, genitourinary anomalies, skeletal malformations, and seizures (~15%). Psychiatric and behavioral abnormalities can include autism spectrum disorders, attention deficit hyperactivity disorder, autistic features, and sleep disturbances.

Sex reversal in an individual associated with a 9p24.3 deletion.

The Catania type of acrofacial dysostosis is characterized by intrauterine growth retardation, short stature, microcephaly, intellectual disability, widow's peak, mandibulofacial dysostosis without cleft palate, ear anomalies, mild pre- and postaxial limb hypoplasia with brachydactyly, mild interdigital webbing, dental anomalies, and cryptorchidism and hypospadias in males (Opitz et al., 1993; Wulfsberg et al., 1996).

Rubinstein-Taybi syndrome (RSTS) is characterized by distinctive facial features, broad and often angulated thumbs and halluces, short stature, and moderate-to-severe intellectual disability. The characteristic craniofacial features are downslanted palpebral fissures, low-hanging columella, high palate, grimacing smile, and talon cusps. Prenatal growth is often normal, then height, weight, and head circumference percentiles rapidly drop in the first few months of life. Short stature is typical in adulthood. Obesity may develop in childhood or adolescence. Average IQ ranges between 35 and 50; however, developmental outcome varies considerably. Some individuals with EP300-RSTS have normal intellect. Additional features include ocular abnormalities, hearing loss, respiratory difficulties, congenital heart defects, renal abnormalities, cryptorchidism, feeding problems, recurrent infections, and severe constipation.

AP-4-associated hereditary spastic paraplegia (HSP), also known as AP-4 deficiency syndrome, is a group of neurodegenerative disorders characterized by a progressive, complex spastic paraplegia with onset typically in infancy or early childhood. Early-onset hypotonia evolves into progressive lower-extremity spasticity. The majority of children become nonambulatory and usually wheelchair bound. Over time spasticity progresses to involve the upper extremities, resulting in a spastic tetraplegia. Associated complications include dysphagia, contractures, foot deformities, dysregulation of bladder and bowel function, and a pseudobulbar affect. About 50% of affected individuals have seizures. Postnatal microcephaly (usually in the -2SD to -3SD range) is common. All have developmental delay. Speech development is significantly impaired and many affected individuals remain nonverbal. Intellectual disability in older children is usually moderate to severe.

Rafiq syndrome (RAFQS) is an autosomal recessive disorder characterized by variably impaired intellectual and motor development, a characteristic facial dysmorphism, truncal obesity, and hypotonia. The facial dysmorphism comprises prominent eyebrows with lateral thinning, downward-slanting palpebral fissures, bulbous tip of the nose, large ears, and a thin upper lip. Behavioral problems, including overeating, verbal and physical aggression, have been reported in some cases. Serum transferrin isoelectric focusing shows a type 2 pattern (summary by Balasubramanian et al., 2019).

The Zaki-Gleeson syndrome is an autosomal recessive neurodevelopmental disorder characterized by profound mental retardation, severe microcephaly, poor growth, cerebellar hypoplasia, and second-degree cardiac conduction defects (Zaki et al., 2011).

SOFT syndrome is characterized by severely short long bones, peculiar facies associated with paucity of hair, and nail anomalies. Growth retardation is evident on prenatal ultrasound as early as the second trimester of pregnancy, and affected individuals reach a final stature consistent with a height age of 6 years to 8 years. Relative macrocephaly is present during early childhood but head circumference is markedly low by adulthood. Psychomotor development is normal. Facial dysmorphism includes a long, triangular face with prominent nose and small ears, and affected individuals have an unusual high-pitched voice. Clinodactyly, brachydactyly, and hypoplastic distal phalanges and fingernails are present in association with postpubertal sparse and short hair. Typical skeletal findings include short and thick long bones with mild irregular metaphyseal changes, short femoral necks, and hypoplastic pelvis and sacrum. All long bones of the hand are short, with major delay of carpal ossification and cone-shaped epiphyses. Vertebral body ossification is also delayed (summary by Sarig et al., 2012).

Microcephalic primordial dwarfism, Dauber type is a rare, genetic developmental defect during embryogenesis characterized by severe pre- and postnatal growth retardation, severe microcephaly, severe developmental delay and intelletual disability, severe adult short stature and facial dysmorphism (incl. hypotelorism, small ears, prominent nose). Other reported features include skeletal anomalies (Madelung deformity, clinodactyly, mild lumbar scoliosis, bilateral hip dysplasia) and seizures. Absence of thelarche and menarche is also associated.

Zellweger syndrome (ZS) is an autosomal recessive multiple congenital anomaly syndrome resulting from disordered peroxisome biogenesis. Affected children present in the newborn period with profound hypotonia, seizures, and inability to feed. Characteristic craniofacial anomalies, eye abnormalities, neuronal migration defects, hepatomegaly, and chondrodysplasia punctata are present. Children with this condition do not show any significant development and usually die in the first year of life (summary by Steinberg et al., 2006). For a complete phenotypic description and a discussion of genetic heterogeneity of Zellweger syndrome, see 214100. Individuals with PBDs of complementation group 12 (CG12, equivalent to CGG) have mutations in the PEX3 gene. For information on the history of PBD complementation groups, see 214100.

Zellweger syndrome (ZS) is an autosomal recessive multiple congenital anomaly syndrome resulting from disordered peroxisome biogenesis. Affected children present in the newborn period with profound hypotonia, seizures, and inability to feed. Characteristic craniofacial anomalies, eye abnormalities, neuronal migration defects, hepatomegaly, and chondrodysplasia punctata are present. Children with this condition do not show any significant development and usually die in the first year of life (summary by Steinberg et al., 2006). For a complete phenotypic description and a discussion of genetic heterogeneity of Zellweger syndrome, see 214100. Individuals with PBDs of complementation group 14 (CG14, equivalent to CGJ) have mutations in the PEX19 gene. For information on the history of PBD complementation groups, see 214100.

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.

Severe intellectual disability-short stature-behavioral abnormalities-facial dysmorphism syndrome is a rare, genetic, syndromic intellectual disability disorder characterized by severe intellectual disability with limited or absent speech and language, short stature, acquired microcephaly, kyphoscoliosis or scoliosis, and behavioral disturbances that include hyperactivity, stereotypy and aggressiveness. Facial dysmorphism, that typically includes sloping forehead, mild synophrys, deep-set eyes, strabismus, anteverted large ears, prominent nose and dental malposition, is also characteristic.

PDE4D haploinsufficiency syndrome is a rare syndromic intellectual disability characterized by developmental delay, intellectual disability, low body mass index, long arms, fingers and toes, prominent nose and small chin.

Any autosomal recessive primary microcephaly in which the cause of the disease is a mutation in the CENPE gene.

Microcephaly and chorioretinopathy-2 is an autosomal recessive developmental disorder characterized by delayed psychomotor development, visual impairment, and short stature (summary by Martin et al., 2014). For a discussion of genetic heterogeneity of microcephaly and chorioretinopathy, see MCCRP1 (251270).

UNC80 deficiency is characterized by hypotonia, strabismus, oral motor dysfunction, postnatal growth deficiency, and developmental delay. The majority of individuals do not learn to walk. All individuals lack expressive language; however, many have expressive body language, and a few have used signs to communicate. Seizures may develop during infancy or childhood. Additional features can include nystagmus, extremity hypertonia, a high-pitched cry, repetitive and self-stimulatory behaviors, constipation, clubfeet, joint contractures, and scoliosis. For most individuals the UNC80 deficiency syndrome is not progressive. Individuals have slow acquisition of skills and do not have a loss of skills suggestive of neurodegeneration.

An asphyxiating thoracic dystrophy that has material basis in homozygous mutation in the CEP120 gene on chromosome 5q23.

Female-restricted X-linked syndromic intellectual developmental disorder-99 (MRXS99F) is an X-linked dominant neurodevelopmental disorder characterized by delayed psychomotor development and mild to moderate intellectual disability. Affected females can have a wide range of additional congenital anomalies, including scoliosis, postaxial polydactyly, mild cardiac or urogenital anomalies, dysmorphic facial features, and mild structural brain abnormalities (summary by Reijnders et al., 2016).

X-linked syndromic intellectual developmental disorder-34 (MRXS34) is an X-linked recessive neurodevelopmental disorder characterized by delayed psychomotor development, intellectual disability with poor speech, dysmorphic facial features, and mild structural brain abnormalities, including thickening of the corpus callosum (summary by Mircsof et al., 2015).

Tonne-Kalscheuer syndrome (TOKAS) is an X-linked recessive multiple congenital anomaly disorder with 2 main presentations. Most patients exhibit global developmental delay apparent from early infancy, impaired intellectual development, speech delay, behavioral abnormalities, and abnormal gait. Affected individuals also have dysmorphic facial features that evolve with age, anomalies of the hands, feet, and nails, and urogenital abnormalities with hypogenitalism. A subset of more severely affected males develop congenital diaphragmatic hernia in utero, which may result in perinatal or premature death. Carrier females may have very mild skeletal or hormonal abnormalities (summary by Frints et al., 2019). Also see Fryns syndrome (229850), an autosomal recessive disorder with overlapping features.

Developmental and epileptic encephalopathy-49 (DEE49) is a severe autosomal recessive neurologic disorder characterized by onset of seizures in the neonatal period, global developmental delay with intellectual disability and lack of speech, hypotonia, spasticity, and coarse facial features. Some patients may have brain calcifications on imaging (summary by Han et al., 2016). For a general phenotypic description and a discussion of genetic heterogeneity of DEE, see 308350.

MRT74 is characterized by intellectual impairment, macrocephaly, and dysmorphic features. Epilepsy with eyelid myoclonus has also been reported (Almuriekhi et al., 2015; Mastrangelo et al., 2020).

Stankiewicz-Isidor syndrome (STISS) is a neurodevelopmental disorder characterized by delayed psychomotor development, intellectual disability, behavioral disorders, mild craniofacial anomalies, and variable congenital defects of the cardiac and/or urogenital systems (summary by Kury et al., 2017).

Junctional epidermolysis bullosa-7 with interstitial lung disease and nephrotic syndrome (JEB7), also known as ILNEB, is an autosomal recessive multiorgan disorder that includes congenital interstitial lung disease, nephrotic syndrome, and epidermolysis bullosa. The respiratory and renal features predominate, and lung involvement accounts for the lethal course of the disease (summary by Has et al., 2012).

NEDDFL is a neurodevelopmental disorder characterized by delayed psychomotor development and impaired intellectual development, poor growth with small head size, dysmorphic facial features, and mild abnormalities of the hands and feet (summary by Stankiewicz et al., 2017).

A rare genetic disorder with characteristics of infantile onset of stagnation and regression of motor and language development resulting in complete lack of communication and purposeful movement. Further neurological manifestations include truncal hypotonia, appendicular spasticity, dystonia, optic disc pallor, peripheral neuropathy and neurogenic bladder. Patients also present multiple contractures, late-onset relative macrocephaly, short stature and facial dysmorphism (including coarse facial features, sloping forehead, thick eyebrows, low-set ears, prominent nose, flat philtrum, and prominent lower lip). Brain imaging at advanced stages shows diffuse abnormal white matter signal and severe atrophy. Sural nerve biopsy reveals decreased myelination.

MRT61 is an autosomal recessive neurodevelopmental disorder characterized by delayed psychomotor development, moderate to severe intellectual disability, and variable dysmorphic facial features. More severely affected patients may develop refractory seizures and have brain abnormalities, including hypoplasia of the corpus callosum (summary by Alwadei et al., 2016).

Seckel syndrome is a rare autosomal recessive disorder characterized by intrauterine growth retardation, dwarfism, microcephaly with mental retardation, and a characteristic 'bird-headed' facial appearance (Shanske et al., 1997). Genetic Heterogeneity of Seckel Syndrome Other forms of Seckel syndrome include SCKL2 (606744), caused by mutation in the RBBP8 gene (604124) on chromosome 18q11; SCKL4 (613676), caused by mutation in the CENPJ gene (609279) on chromosome 13q12; SCKL5 (613823), caused by mutation in the CEP152 gene (613529) on chromosome 15q21; SCKL6 (614728), caused by mutation in the CEP63 gene (614724) on chromosome 3q22; SCKL7 (614851), caused by mutation in the NIN gene (608684) on chromosome 14q22; SCKL8 (615807), caused by mutation in the DNA2 gene (601810) on chromosome 10q21; SCKL9 (616777), caused by mutation in the TRAIP gene (605958) on chromosome 3p21; SCKL10 (617253), caused by mutation in the NSMCE2 gene (617246) on chromosome 8q24; and SCKL11 (620767), caused by mutation in the CEP295 gene (617728) on chromosome 11q21. The report of a Seckel syndrome locus on chromosome 14q, designated SCKL3, by Kilinc et al. (2003) was found to be in error; see History section.

Rubinstein-Taybi syndrome (RSTS) is characterized by distinctive facial features, broad and often angulated thumbs and halluces, short stature, and moderate-to-severe intellectual disability. The characteristic craniofacial features are downslanted palpebral fissures, low-hanging columella, high palate, grimacing smile, and talon cusps. Prenatal growth is often normal, then height, weight, and head circumference percentiles rapidly drop in the first few months of life. Short stature is typical in adulthood. Obesity may develop in childhood or adolescence. Average IQ ranges between 35 and 50; however, developmental outcome varies considerably. Some individuals with EP300-RSTS have normal intellect. Additional features include ocular abnormalities, hearing loss, respiratory difficulties, congenital heart defects, renal abnormalities, cryptorchidism, feeding problems, recurrent infections, and severe constipation.

Ververi-Brady syndrome (VEBRAS) is characterized by mild developmental delay, mildly impaired intellectual development and speech delay, and mild dysmorphic facial features. Affected individuals can usually attend mainstream schools with support, and may also show autistic features (summary by Ververi et al., 2018).

Alacrima, achalasia, and impaired intellectual development syndrome (AAMR) is an autosomal recessive disorder characterized by onset of these 3 main features at birth or in early infancy. More variable features include hypotonia, gait abnormalities, anisocoria, and visual or hearing deficits. The disorder shows similarity to the triple A syndrome (231550), but patients with AAMR do not have adrenal insufficiency (summary by Koehler et al., 2013). See also 300858 for a phenotypically similar disorder that shows X-linked inheritance.

Proteasome-associated autoinflammatory syndrome-1 (PRAAS1) is an autosomal recessive disorder characterized by early childhood onset of annular erythematous plaques on the face and extremities with subsequent development of partial lipodystrophy and laboratory evidence of immune dysregulation. More variable features include recurrent fever, severe joint contractures, muscle weakness and atrophy, hepatosplenomegaly, basal ganglia calcifications, and microcytic anemia (summary by Agarwal et al., 2010; Kitamura et al., 2011; Arima et al., 2011). This disorder encompasses Nakajo-Nishimura syndrome (NKJO); joint contractures, muscular atrophy, microcytic anemia, and panniculitis-induced lipodystrophy (JMP syndrome); and chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperature syndrome (CANDLE). Among Japanese patients, this disorder is best described as Nakajo-Nishimura syndrome, since both Nakajo (1939) and Nishimura et al. (1950) contributed to the original phenotypic descriptions. Genetic Heterogeneity of Proteasome-Associated Autoinflammatory Syndrome See also PRAAS2 (618048), caused by mutation in the POMP gene (613386) on chromosome 13q12; PRAAS3 (617591), caused by mutation in the PSMB4 gene (602177) on chromosome 1q21; PRAAS4 (619183), caused by mutation in the PSMG2 gene (609702) on chromosome 18p11; PRAAS5 (619175), caused by mutation in the PSMB10 gene (176847) on chromosome 16q22; and PRAAS6 (620796), caused by mutation in the PSMB9 gene (177045) on chromosome 6p21.

Neurodevelopmental disorder with spasticity and poor growth (NEDSG) is an autosomal recessive disorder characterized by severe early-onset encephalopathy with progressive microcephaly (Nahorski et al., 2018).

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

Snijders Blok-Campeau syndrome (SNIBCPS) is an autosomal dominant neurodevelopmental disorder characterized by global developmental delay with impaired intellectual development and delayed speech acquisition. Affected individuals tend to have expressive language deficits, with speech apraxia and dysarthria. Other features include macrocephaly and characteristic facial features, such as prominent forehead and hypertelorism, hypotonia, and joint laxity. The severity of the neurologic deficits and presence of nonneurologic features is variable (summary by Snijders Blok et al., 2018).

Mullegama-Klein-Martinez syndrome (MKMS) is an X-linked recessive disorder with features of microcephaly, microtia, hearing loss, developmental delay, dysmorphic features, congenital heart defect, and digit abnormalities. Females are generally affected more severely than males (Mullegama et al., 2019).

IDDCDF is an autosomal recessive syndromic neurodevelopmental disorder characterized by globally impaired development with intellectual disability and speech delay, congenital cardiac malformations, and dysmorphic facial features. Additional features, such as distal skeletal anomalies, may also be observed (Stephen et al., 2018).

Short stature and microcephaly with genital anomalies (SSMGA) is characterized by severe growth failure, with extreme short stature, microcephaly, and delayed and dissociated bone age. Global psychomotor developmental delay may be present, although the brain appears structurally normal. Pubertal delay and genital anomalies have been observed (Hung et al., 2017).

Nabais Sa-de Vries syndrome type 2 (NSDVS2) is characterized by global developmental delay apparent from birth and distinctive dysmorphic facial features. Most patients have additional anomalies, including congenital heart defects, sleep disturbances, hypotonia, and variable endocrine abnormalities, such as hypothyroidism (summary by Nabais Sa et al., 2020).

Developmental and epileptic encephalopathy-87 (DEE87) is a neurologic disorder characterized by global developmental delay, hypotonia, and onset of frequent refractory seizures or infantile spasms between 6 and 15 months of age. Affected individuals have severely impaired motor and cognitive development with little or absent speech and poor visual tracking. More variable features include facial dysmorphisms, joint laxity, and nonspecific brain imaging findings (summary by Chung et al., 2020).

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.

Tolchin-Le Caignec syndrome (TOLCAS) is a developmental disorder characterized by mildly to moderately impaired intellectual development and behavioral problems, such as autism, ADHD, labile mood, and aggressive episodes. Many patients have bony abnormalities, including osteochondroma, craniosynostosis, dysmorphic facies, arachnodactyly, and large head circumference. Rarely, additional congenital anomalies may also be observed. These additional features and the bony defects are highly variable (summary by Tolchin et al., 2020).

Neurodevelopmental disorder with cerebral atrophy and facial dysmorphism (NEDCAFD) is an autosomal recessive disorder characterized by global developmental delay apparent from birth. Affected individuals have hypotonia with inability to walk and severely impaired intellectual development with absent language. Most patients have variable dysmorphic facial features including prominent eyes, protruding and low-set ears, and thin upper lip. Brain imaging shows cerebral atrophy, corpus callosum hypoplasia, and a simplified gyral pattern (summary by Rasheed et al., 2021).

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).

DEGCAGS syndrome is an autosomal recessive syndromic neurodevelopmental disorder characterized by global developmental delay, coarse and dysmorphic facial features, and poor growth and feeding apparent from infancy. Affected individuals have variable systemic manifestations often with significant structural defects of the cardiovascular, genitourinary, gastrointestinal, and/or skeletal systems. Additional features may include sensorineural hearing loss, hypotonia, anemia or pancytopenia, and immunodeficiency with recurrent infections. Death in childhood may occur (summary by Bertoli-Avella et al., 2021).

Neurodevelopmental disorder with hypotonia and dysmorphic facies (NEDHYDF) is characterized by global developmental delay and hypotonia apparent from birth. Affected individuals have variably impaired intellectual development, often with speech delay and delayed walking. Seizures are generally not observed, although some patients may have single seizures or late-onset epilepsy. Most patients have prominent dysmorphic facial features. Additional features may include congenital cardiac defects (without arrhythmia), nonspecific renal anomalies, joint contractures or joint hyperextensibility, dry skin, and cryptorchidism. There is significant phenotypic variability in both the neurologic and extraneurologic manifestations (summary by Tan et al., 2022).

Pontocerebellar hypoplasia type 16 (PCH16) is an autosomal recessive severe neurodevelopmental disorder characterized by hypotonia and severe global developmental delay apparent from early infancy. Although the severity of the disorder is variable, most affected individuals achieve only a few, if any, developmental milestones. Most are unable to walk or speak, have eye abnormalities with poor visual contact, and develop early-onset epilepsy. Other features may include stereotypic movements, spasticity, and progressive microcephaly. Brain imaging shows pontocerebellar hypoplasia, often with thin corpus callosum, atrophy of the thalamus and basal ganglia, enlarged ventricles, and white matter abnormalities (summary by Ucuncu et al., 2020). For a phenotypic description and a discussion of genetic heterogeneity of PCH, see PCH1A (607596).

Cerebellar ataxia, brain abnormalities, and cardiac conduction defects (CABAC) is an autosomal recessive primarily neurologic disorder with variable manifestations. Common features included infantile-onset hypotonia, poor motor development, poor feeding and overall growth, and ataxic gait due to cerebellar ataxia. Other features include dysarthria, nystagmus, variable ocular anomalies, spasticity, hyperreflexia, and nonspecific dysmorphic features. Most, but not all, patients have global developmental delay with impaired intellectual development and speech delay. Brain imaging shows cerebellar hypoplasia, often with brainstem hypoplasia, enlarged ventricles, delayed myelination, and thin corpus callosum. A significant number of patients develop cardiac conduction defects in childhood or adolescence, often requiring pacemaker placement (summary by Slavotinek et al., 2020).

Nonphotosensitive trichothiodystrophy-8 (TTD8) is characterized by brittle hair and nails and scaly skin, accompanied by failure to thrive, microcephaly, and neuromotor developmental delay. Hair analysis shows low sulfur content, and skin fibroblasts demonstrate normal DNA repair efficiency after UV irradiation (Botta et al., 2021). For a general phenotypic description and discussion of genetic heterogeneity of trichothiodystrophy, see TTD1 (601675).

Atelis syndrome-1 (ATELS1) is an autosomal recessive neurodevelopmental disorder characterized by global developmental delay with learning difficulties and poor overall growth with short stature and microcephaly. Most patients have anemia, some have immunologic defects, and some have congenital heart septal defects. More variable features may include hypotonia, dysmorphic facial features, skin pigmentary anomalies, and mild skeletal defects. Patient cells show multiple chromosomal abnormalities due to impaired DNA replication and disrupted mitosis (Grange et al., 2022). See also ATELS2 (620185), caused by mutation in the SMC5 gene (609386) on chromosome 9q21. For a discussion of genetic heterogeneity of MVA, see MVA1 (257300).

Atelis syndrome-2 (ATELS2) is an autosomal recessive disorder characterized by poor overall growth with microcephaly and short stature, dysmorphic facial features, and congenital cardiac defects. Additional more variable features may include hematologic abnormalities, variable ocular abnormalities, motor delay, and anxiety. Patient cells exhibit a unique chromosomal instability phenotype consisting of segmented and dicentric chromosomes with mosaic variegated hyperploidy (Grange et al., 2022). See also ATELS1 (620184), caused by mutation in the SLF2 gene (610348). For a discussion of genetic heterogeneity of MVA, see MVA1 (257300).

Neurodevelopmental disorder with hypotonia, dysmorphic facies, and skin abnormalities (NEDHFS) is an autosomal recessive disorder characterized by severe global developmental delay with impaired intellectual development and poor or absent speech. Affected individuals have dysmorphic facies, including large abnormally shaped ears and strabismus, hypotonia, and dry skin with keratosis pilaris. Some patients develop seizures. Metabolic studies are unremarkable (Morava et al., 2021).

Neurodevelopmental disorder with poor growth, large ears, and dysmorphic facies (NEDGEF) is an autosomal recessive disorder characterized by these features as well as hypotonia and global developmental delay with impaired intellectual development. The severity is variable, even within families. Death in early childhood has been reported in 1 family (Alsaif et al., 2021).

Tessadori-Bicknell-van Haaften neurodevelopmental syndrome-3 (TEBIVANED3) is characterized by global developmental delay with poor overall growth, impaired intellectual development, and speech difficulties. More variable features include hypotonia, microcephaly, and dysmorphic facies. The severity and manifestations of the disorder are highly variable (Tessadori et al., 2022). For a discussion of genetic heterogeneity of Tessadori-Bicknell-van Haaften neurodevelopmental disorder, see TEBIVANED1 (619758).

Neurodevelopmental disorder with microcephaly and speech delay, with or without brain abnormalities (NEDMSBA) is an autosomal recessive disorder characterized by global developmental delay, hypotonia, delayed or absent walking, impaired intellectual development, and poor or absent speech, apparent from early infancy. Affected individuals have postnatal progressive microcephaly and may show poor overall growth and dysmorphic facial features. Additional more variable features include cortical visual impairment, seizures, hypotonia, spasticity, and sensorineural deafness. Brain imaging is abnormal in most patients, showing myelination defects, cortical atrophy, or thin corpus callosum. There is phenotypic variability, even within families (Bogershausen et al., 2022; Lin et al., 2022).

Autosomal dominant intellectual developmental disorder-73 (MRD73) is a highly variable neurodevelopmental disorder characterized by impaired intellectual development that ranges from mild to severe, speech delay, behavioral abnormalities, and nonspecific dysmorphic facial features (Janssen et al., 2022).