Freeman-Sheldon syndrome (FSS), or DA2A, is phenotypically similar to DA1. In addition to contractures of the hands and feet, FSS is characterized by oropharyngeal abnormalities, scoliosis, and a distinctive face that includes a very small oral orifice (often only a few millimeters in diameter at birth), puckered lips, and an H-shaped dimple of the chin; hence, FSS has been called 'whistling face syndrome.' The limb phenotypes of DA1 and FSS may be so similar that they can only be distinguished by the differences in facial morphology (summary by Bamshad et al., 2009). For a general phenotypic description and a discussion of genetic heterogeneity of distal arthrogryposis, see DA1 (108120).

Lenz-Majewski hyperostotic dwarfism is a rare condition characterized by intellectual disability, sclerosing bone dysplasia, distinct craniofacial and dental anomalies, loose skin, and distal limb anomalies, particularly brachydactyly and symphalangism. Patients have multiple radiographic abnormalities due to progressive generalized hyperostosis that affects the cranium, vertebrae, and diaphyses of tubular bones, leading to severe growth retardation (summary by Sousa et al., 2014).

Osteoglophonic dysplasia (OGD) is characterized by rhizomelic dwarfism, nonossifying bone lesions, craniosynostosis, prominent supraorbital ridge, and depressed nasal bridge (summary by White et al., 2005).

Microphthalmia with linear skin defects (MLS) syndrome is characterized by unilateral or bilateral microphthalmia and/or anophthalmia and linear skin defects, usually involving the face and neck, which are present at birth and heal with age, leaving minimal residual scarring. Other findings can include a wide variety of other ocular abnormalities (e.g., corneal anomalies, orbital cysts, cataracts), central nervous system involvement (e.g., structural anomalies, developmental delay, infantile seizures), cardiac concerns (e.g., hypertrophic or oncocytic cardiomyopathy, atrial or ventricular septal defects, arrhythmias), short stature, diaphragmatic hernia, nail dystrophy, hearing impairment, and genitourinary malformations. Inter- and intrafamilial variability is described.

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).

Hand-foot-genital syndrome (HFGS) is characterized by limb malformations and urogenital defects. Mild-to-severe bilateral shortening of the thumbs and great toes, caused primarily by shortening of the distal phalanx and/or the first metacarpal or metatarsal, is the most common limb malformation and results in impaired dexterity or apposition of the thumbs. Urogenital malformations include abnormalities of the ureters and urethra and various degrees of incomplete müllerian fusion in females, and hypospadias of variable severity with or without chordee in males. Vesicoureteral reflux, recurrent urinary tract infections, and chronic pyelonephritis may occur; fertility is normal.

Martin-Probst syndrome (MRXSMP) is characterized by congenital sensorineural hearing loss, mild to severe cognitive impairment, short stature, and facial dysmorphism, including telecanthus, hypertelorism, epicanthic folds, broad mouth, and low-set ears. Variable features include renal and genitourinary abnormalities and late-onset pancytopenia (Martin et al., 2000).

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

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

Palatal anomalies-widely spaced teeth-facial dysmorphism-developmental delay syndrome is a rare, genetic multiple congenital anomalies/dysmorphic syndrome characterized by global developmental delay, axial hypotonia, palate abnormalities (including cleft palate and/or high and narrow palate), dysmorphic facial features (including prominent forehead, hypertelorism, downslanting palpebral fissures, wide nasal bridge, thin lips and widely spaced teeth), and short stature. Additional manifestations may include digital anomalies (such as brachydactyly, clinodactyly, and hypoplastic toenails), a single palmar crease, lower limb hypertonia, joint hypermobility, as well as ocular and urogenital anomalies.

RERE-related disorders are characterized by neurodevelopmental problems with or without structural anomalies of the eyes, heart, kidneys, and genitourinary tract and mild sensorineural hearing loss. Hypotonia and feeding problems are common among affected individuals. Developmental delay and intellectual disability range from mild to profound. Behavior problems may include attention-deficit/hyperactivity disorder, self-injurious behavior, and autism spectrum disorder. A variety of eye anomalies (coloboma, optic nerve anomalies, microphthalmia, and/or Peter's anomaly) and vision issues (myopia, anisometropia, astigmatism, exotropia, esotropia) have been reported. Congenital heart defects, most commonly septal defects, have also been described. Genitourinary abnormalities include vesicoureteral reflux, and cryptorchidism and hypospadias in males. Sensorineural hearing loss can be unilateral or bilateral.

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).

Individuals with PPP1R12A-related urogenital and/or brain malformation syndrome (UBMS) usually present with multiple congenital anomalies, commonly including brain and/or urogenital malformations. The brain abnormalities are variable, with the most severe belonging to the holoprosencephaly spectrum and associated with moderate-to-profound intellectual disability, seizures, and feeding difficulties. In individuals without brain involvement, variable degrees of developmental delay and/or intellectual disability may be present, although normal intelligence has been seen in a minority of affected individuals. Eye abnormalities and skeletal issues (kyphoscoliosis, joint contractures) can also be present in individuals of either sex. Regardless of the presence of a brain malformation, affected individuals with a 46,XY chromosome complement may have a disorder of sex development (DSD) with gonadal abnormalities (dysgenetic gonads or streak gonads). Individuals with a 46,XX chromosome complement may have varying degrees of virilization (clitoral hypertrophy, posterior labial fusion, urogenital sinus).

Microcephaly, developmental delay, and brittle hair syndrome (MDBH) is a multisystem disorder with clinical variability. Affected individuals show cognitive and motor disabilities, as well as some degree of fine, brittle hair with microscopic shaft abnormalities. Other shared features include failure to thrive in early childhood and short stature, with some patients exhibiting feeding difficulties and hepatic steatosis (Kuo et al., 2019).

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-craniofacial syndrome with variable renal and cardiac abnormalities (NECRC) is an autosomal dominant disorder characterized by dysmorphic craniofacial features associated with mild developmental delay, mildly impaired intellectual development or learning difficulties, speech delay, and behavioral abnormalities. About half of patients have congenital anomalies of the kidney and urinary tract (CAKUT) and/or congenital cardiac defects, including septal defects (Connaughton et al., 2020).

Chilton-Okur-Chung neurodevelopmental syndrome (CHOCNS) is characterized mainly by global developmental delay with variably impaired intellectual development and occasional speech delay. Most patients have behavioral abnormalities, including autism spectrum disorder, ADHD, and aggression. About half of patients have dysmorphic facial features, and about half have nonspecific brain abnormalities, including thin corpus callosum. Rare involvement of other organ systems may be present. At least 1 child with normal development at age 2.5 years has been reported (Chilton et al., 2020).

Neurodevelopmental disorder with hypotonia and speech delay, with or without seizures (NEDHSS) is characterized by global developmental delay, impaired intellectual development with poor or absent speech, and fine and gross motor delay. Most affected individuals are severely affected and may be unable to walk, have feeding difficulties requiring tube-feeding, and develop early-onset seizures. Additional features may include cortical blindness and nonspecific structural brain abnormalities. Rare individuals present only with hypotonia and mild developmental delay (Paul et al., 2023).