Hereditary multiple exostoses (HME) is a rare medical condition in which multiple bony spurs or lumps (also known as exostoses, or osteochondromas) develop on the bones of a child. HME is synonymous with Multiple hereditary exostoses and Multiple osteochondromatosis, which is the preferred term used by the World Health Organization.
HME is estimated to occur in 1 in 50,000 people. It is characterized by the growth of cartilage-capped benign bone tumours around areas of active bone growth, particularly the metaphysis of the long bones. HME can lead to the shortening and bowing of bones, as such affected individuals often have a short stature. Depending on their location the exostoses can cause the following problems: pain or numbness from nerve compression, vascular compromise, inequality of limb length, irritation of tendon and muscle, as well as a limited range of motion at the joints upon which they encroach. Generally, when a person with HME reaches maturity, and their bones stop growing, the exostoses also stop growing. A person with HME has an increased risk of developing a rare form of bone cancer called chondrosarcoma as an adult. The reported rate of transformation ranges from as low as 0.57% to as high as 8.3% of people with HME.
