hereditary multiple exostoses, a rare familial dyschondroplastic disease in which bony protuberances form on the shafts of the long bones and eventually develop into caps of cartilage covering the ends of the bones. The affected joints lose their mobility, and the bones stop growing. The disease begins in childhood and has no cure. Very rarely a chondrosarcoma may develop from the cap of an exostosis. See also Ollier’s dyschondroplasia.
