Clinical features include head (macrocephaly,
hypertelorism, prominent forehead and occiput, down-slanting palpebral fissure,
depressed nasal bridge, low-set ears, narrow palate, short neck), central nervous system
(hydrocephalus, hypoplastic cerebellar vermis, posterior fossa cyst/dilated fourth
ventricle [Dandy-Walker malformation], cranial nerve palsies, nystagmus, truncal
ataxia and mild to moderate growth and psychomotor retardation), heart (wide
range of anomalies from cleft mitral valve to complete atrioventricular
defect), and skeleton (first rib aplasia, camptodactyly of fingers, hip dislocation,
hemivertebra, hypoplasia of terminal phalanges, micronychia). Other
clinical signs include hypospadias, coloboma of the iris and/or retina, congenital
glaucoma, optic nerve atrophy, malrotation of the gut, anal atresia,
hydronephrosis, and immunodeficiency.