Hereditary multiple osteochondral exostosis

Osteochondromas are benign tumors commonly seen at the ends of growth plates. Knee and shoulder regions are most commonly affected. Pathologically these are bony outgrowths with a cartilaginous cap. The X-ray appearance of an osteochondroma is that of a pedunculated or sessile bony excrescence with well-defined margins.

Hereditary multiple osteochondral exostosis (HMOCE, a.k.a. multiple osteochondromatosis) is a rare, autosomal dominant disease in which there is occurrence of multiple osteochondromas. More than half of affected patients have symptoms by the age of 5 years. Presenting symptoms include bony bumps that may be painless or have pain induced by pressure on surrounding soft tissue structures. There may be short stature, limb-length discrepancies, valgus deformity of the knee and ankle, bowing of the radius with ulnar deviation of the wrist, and subluxation of the radiocapitellar joint. The ulna and fibula are involved more commonly leading to differential growth and angular deformities. Malignant transformation is seen in about 25 % of patients with HMOCE and the resulting neoplasms are usually low grade chondrosarcomas. This is remarkable compared to the 1-2% risk seen with isolated osteochondromas.

Treatment is surgical excision of large or symptomatic tumors. Regular self and physician follow up is important due to the risk of sarcomatous transformation. Outcome is generally good with follow up and surgical resection of suspicious lesions.