Multiple peripheral nerve compressions related to malignantly transformed hereditary multiple exostoses.

Autosomal dominantly transmitted hereditary multiple exostoses is an uncommon disorder consisting of multiple projections of bone capped by cartilage. The lesions are most numerous in the metaphyses of long bones but may appear on flat bones. Sarcomatous transformation occurs in 1-25% of patients. We report a 33-year-old man with sciatica, previously diagnosed as hereditary multiple exostoses, presenting with multiple peripheral nerve compressions. Electrodiagnostic studies showed profound axon-loss multiple neuropathies involving the sciatic, superior gluteal, and inferior gluteal nerves. Magnetic resonance imaging of the left pelvis showed a large mass in the sacral area that was suggestive of a chondrosarcoma. An open intralesional excision biopsy confirmed chondrosarcoma transformed from chondromatosis. Excision of the lesion was effective in eliminating the impingement of nerves and retarding progressive osseous growth. We suggest that malignant transformation be suspected in cases with focal compression neuropathy of patients known to have multiple exostoses. Osteochondroma as a possible cause for compression neuropathy is discussed.