Hereditary Multiple Exostoses

**Semantic type:** Disease or Syndrome

**Definition:** Hereditary disorder transmitted by autosomal dominant genes (EXT1-3) and characterized by multiple exostoses (multiple osteochondromas) near the ends of long bones. The genetic abnormality results in a defect in the osteoclastic activity at the metaphyseal ends of the bone during the remodeling process in childhood or early adolescence. The metaphyses develop benign, bony outgrowths often capped by cartilage. A small number undergo neoplastic transformation.