rare congenital, hereditary disorder characterized by collarbones that are absent or reduced in size, skull abnormalities, and abnormal dentition. The shoulders may sometimes touch in front of the chest, and certain facial bones are underdeveloped or missing. Cranial sutures are late in fusing, and the skull is round and the eyes are set wide apart. Other bones, especially the radius (in the forearm), pelvis, hip joint, and vertebrae, may be malformed. Deciduous teeth are late in falling out, and, as a result, the permanent teeth are often abnormal. Individuals are not disabled beyond difficulty in walking, and life expectancy is normal.