Denouement and Discussion
Hereditary Multiple Exostoses (Diaphyseal Aclasis)
The exostoses are usually present by the age of 10 years but, on occasion, may be noted in infancy. They vary in size and location, with the most common sites being the scapula, ends of the long bones, ribs, and iliac crest. Following puberty, growth usually stops, and no new lesions appear. The exostoses can affect the growth of the long bones, resulting in various deformities, such as bowing of the radius, shortening of the ulna, radiohumeral dislocation, genu valgum, and valgus deformities of the ankles. Other skeletal abnormalities include scoliosis, short stature, and thoracic and pelvic deformities. Malignant degeneration of the exostoses (chondrosarcomas) takes place in approximately 5% to 10% of the patients. They are usually diagnosed in the early 30s age group, and most often are located in the pelvis and the femur. On roentgenographic examination, the exostoses are
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