Features of an osteodysplasia are among the most striking in this syndrome. Short stature, brachydactyly, delayed bone age, osteoporosis, and hypoplasia of the acetabulae and iliac alae are usually present. Birth weight is often low. Joints may be hyperflexible as part of the generalized hypotonia. The eyes are deep-set, the nasal bridge is prominent, the midface is flat, and the supraorbital ridges are prominent giving the face a rather coarse look. Prognathism with a prominent lower lip and dental malocclusion reinforce this appearance. Seizures beginning in early childhood may be difficult to control. Most patients have severe psychomotor retardation and never acquire speech.