Craniofacial dysmorphism with
macrocephaly, hypertelorism, frontal bossing, bulbous nose, depressed
premaxillary region, prognathism, and low-set ears. Moderate-to-severe mental
retardation. Musculoskeletal abnormalities include hyperextensible
joints, osteoporosis and osteosclerosis, and syndactyly of toes.