The facial features are reported to be characteristic but there are few distinctive signs. The face is often broad and round, the nose is beaked, the mouth is small, and the lower lip appears to pout and protrudes beyond a short upper lip. Smiles have been described as 'grimacing'. It is common for the columella to protrude beyond the alae nasi. The palate is narrow and highly arched and the laryngeal walls collapse easily which may lead to feeding problems and respiratory difficulties. The ears may be rotated posteriorly. The anterior hairline can appear low.
Among the more distinctive signs are the broad thumbs and great toes which are often deviated medially. However, the distal phalanges of all fingers may be broad as well. Bone fractures are common and patellar dislocations can be present as seen in the first two decades of life. Hypotonia is a feature. Numerous dental anomalies have been reported including crowded teeth, enamel hypoplasia, crossbite, and abnormal numbers of teeth.
Developmental delays are common. Infancy and childhood milestones are often delayed. Many patients have cognitive delays and some are mildly retarded. Postnatal growth is subnormal and obesity is common. A third of patients have a cardiac abnormality including septal defects, valvular defects, coarctation of the aorta, pulmonic stenosis, and patent ductus arteriosus. Renal abnormalities occur frequently and almost all males have undescended testes. Patients are at increased risk of tumors, both malignant and benign, many of which occur in the central nervous system. Other problems are constipation and hearing loss.