An inherited skeletal dysplasia resulting in an excessive deposition of endosteal bone throughout the skeleton. It is characterized by enlargement of the lower jaw and thickening of the long bones and the top of the skull. The face may appear swollen with some facial paralysis and deafness. There may also be widening of the bridge of the nose and angles of the mandible. The symptoms are not painful and there is no bone tenderness. It was first described by Van Buchem, a Dutch physician, in 1955. See also hyperostosis.