SMARCA2-related Nicolaides-Baraitser syndrome (SMARCA2-NCBRS) is characterized by commonly shared dysmorphic features including sparse scalp hair, prominence of the interphalangeal joints and distal phalanges due to decreased subcutaneous fat, characteristic coarse facial features, microcephaly (typically acquired), seizures, and developmental delay / intellectual disability. Developmental delay / intellectual disability is severe in nearly half of affected individuals, moderate in one third, and mild in the remainder. Nearly one third never develop speech or language skills. Seizures are of various types and can be difficult to manage, requiring multiple anti-seizure medications to achieve reasonable control. Regression or lack of developmental progress has been noted with the onset of seizures in some affected individuals. Behavioral issues can include autistic-like features (perseveration, hyperacusis), with a minority of affected individuals being diagnosed clinically with an autism spectrum disorder. Cryptorchidism is common in males. About half of affected individuals have growth deficiency and short stature. Delayed tooth eruption with hypo- or oligodontia has also been reported. Radiographic findings may include cone-shaped epiphyses, metaphyseal flaring of the phalanges, and shortening of the phalanges, metacarpals, and/or metatarsals (especially of the 4th and 5th rays) of the hands; platyspondyly; flat intervertebral disc space; and pelvic/femoral anomalies. Rare findings include conductive hearing loss, refractive error / astigmatism, and congenital heart defects.

Extreme hirsutism with gingival fibromatosis follows a dominant pattern of inheritance (Weski, 1920; Garn and Hatch, 1950). There is no necessary relationship between the age of development of the gingival changes and the hypertrichosis. The latter may be present at birth but often appears at puberty (Anderson et al., 1969). For a discussion of genetic heterogeneity of congenital generalized hypertrichosis, see HTC1 (145701).

CTCF-related disorder is characterized by developmental delay / intellectual disability (ranging from mild to severe), with both speech and motor delays being common; feeding difficulties, including dysphagia, and other gastrointestinal issues (gastroesophageal reflux disease and/or irritable bowel syndrome) that can lead to growth deficiency; hypotonia; eye anomalies (strabismus and/or refractive errors); scoliosis; nonspecific dysmorphic features; sleep disturbance; tooth anomalies (crowded teeth and/or abnormal decay); and, less commonly, other congenital anomalies (cleft palate, gastrointestinal malrotation, genitourinary anomalies, and congenital heart defects, including aortic ectasia). Short stature, seizures, hearing loss, recurrent infections, microcephaly, and autistic features have also been described in a minority of affected individuals. At least four reported individuals with CTCF-related disorder developed Wilms tumor, one of whom had bilateral Wilms tumor. However, there is no clear evidence of a significant predisposition for the development of cancer in individuals with CTCF-related disorder at this time.

An autosomal dominant condition caused by mutation(s) in the MYT1L gene, encoding myelin transcription factor 1-like protein. It is characterized by intellectual disability and mild dysmorphic facial features.

Autosomal recessive cutis laxa type IIC (ARCL2C) is characterized by generalized skin wrinkling with sparse subcutaneous fat and dysmorphic progeroid facial features. Most patients also exhibit severe hypotonia as well as cardiovascular involvement (summary by Van Damme et al., 2017). For a general phenotypic description and a discussion of genetic heterogeneity of autosomal recessive cutis laxa, see ARCL1A (219100).

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

Autosomal recessive spinocerebellar ataxia-20 is a neurodevelopmental disorder characterized by severely delayed psychomotor development with poor or absent speech, wide-based or absent gait, coarse facies, and cerebellar atrophy (summary by Thomas et al., 2014).

Shukla-Vernon syndrome (SHUVER) is an X-linked recessive neurodevelopmental disorder characterized by global developmental delay, variably impaired intellectual development, and behavioral abnormalities, including autism spectrum disorder and ADHD. Dysmorphic features are common and may include tall forehead, downslanting palpebral fissures, and tapering fingers. Some patients may have seizures and/or cerebellar atrophy on brain imaging. Carrier mothers may have mild manifestations, including learning disabilities (summary by Shukla et al., 2019).

Autosomal recessive intellectual developmental disorder-72 (MRT72) is characterized by moderately to severely impaired intellectual development, microcephaly, and facial dysmorphism. Some patients may have seizures (Hu et al., 2019).

Stuve-Wiedemann syndrome is an autosomal recessive disorder characterized by bowing of the long bones and other skeletal anomalies, episodic hyperthermia, respiratory distress, and feeding difficulties usually resulting in early death (Dagoneau et al., 2004). See also 'classic' Schwartz-Jampel syndrome type 1 (SJS1; 255800), a phenotypically similar but genetically distinct disorder caused by mutation in the HSPG2 gene (142461) on chromosome 1p36. Genetic Heterogeneity of Stuve-Wiedemann Syndrome Stuve-Wiedemann syndrome-2 (STWS2; 619751) is caused by mutation in the IL6ST gene (600694) on chromosome 5q11.

Megalencephaly-polydactyly syndrome (MPAPA) is an autosomal dominant disorder characterized by megalencephaly, ventriculomegaly, postaxial polydactyly, and, notably, neuroblastoma during infancy (summary by Nishio et al., 2023).