Discussion Author(s): Rahim Fazel
â€¢ Hereditary multiple exostoses (HME), also known as osteochondromatosis, is a highly genetically associated disorder of cartilage-covered bony excrescences that arises from the surface of multiple bones. Osteochondromas, which are the most common bone tumors in children, may be solitary or multiple, and they may arise spontaneously or as a result of previous osseous trauma, generally speaking. An osteochondroma can affect any bone preformed in cartilage. However, most osteochondromas arise from the metaphyseal region of tubular bones.
â€¢ HME is an inherited, autosomal dominant disorder that involves mutations of at least 3 different EXT genes which are mostly tumor suppressor genes in their functions. More specifically, changes in EXT1 and EXT23 seem to be the most common in HME. Patients with HME can have anywhere from two to hundreds of osteochromatous lesions in the body. Most of these are discovered incidentally in children and adolescents, or if there is a slow growing palpable lesion that is being evaluated. The most common locations where the bony lumps are discovered are on the tibia and the scapulae. Approximately 1 person out of 50,000 is likely to be affected by this condition. 90% of studied patients have had an associated family history of HME. This condition is more frequently found in the white population than other races with males and females being equally affected.
â€¢ A higher incidence of HME has been described in isolated communities, such as the Chamorros of Guam or the Ojibwa Indian community in Manitoba, Canada. These populations have a prevalence of 100 and 1310 cases per 100,000 populations, respectively.1
â€¢ Some complications of osteochondromas include fracture, deformities, injury to adjacent vascular or neurologic structures, and malignant transformation. Additionally, the formation of a bursal compartment surrounding a large osteochondroma is common. These may eventually become inflamed due to friction points in mobile bony segments such as the scapulae and distal femur. In addition, a large, pedunculated osteochondroma may be exposed to trauma and fracture.
â€¢ Malignant degeneration occurs in 1-25% of cases and should be suspected if an exostosis rapidly increases in size, particularly in adult patients whom bony growth has ceased. Pain is also a common presentation with malignant transformation, but rarely nerve compression can be the presenting complaint. The mean age at diagnosis is reported to be 31 years. Osteochondromas that continue to grow after puberty should raise the possibility of chondrosarcomatous transformation. PET imaging has shown some promise in demonstrating malignant transformation.2 Alternatively, it is also possible for some osteochondromatous lesions to regress.
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