The main features are central nervous system malformations consisting
usually of occipital encephalocele (with holoprosencephaly, agenesis of
corpus callosum and/or hydrocephalus); seizures; postaxial polydactyly always involving the hand
and occasionally the feet and polycystic kidneys; other urologic anomalies include absent or hypoplastic ureters or
bladder. Often the liver shows cystic changes with duct proliferation and
fibrosis. Other anomalies include microcephaly, microphthalmia or
anophthalmia, cleft lip and/or palate, genital anomalies, lung hypoplasia,
and congenital heart disease such as atrial septal defect (ASD), ventricular septal defect (VSD),
coarctation of the aorta, and patent ductus arteriosus (PDA). Patients also present a
typical “Meckel appearance” with micrognathia, flat nose, hypertelorism, a
sloping forehead, wide mouth with full lips, low-set ears, and short neck.