Diaphyseal aclasis

Case contributed by Mohamed Salah Ayyad
Diagnosis almost certain


Lower limb deformities.

Patient Data

Age: 15 years
Gender: Male

Multiple sessile and pedunculated bony outgrowths are seen arising from the proximal and distal femoral shafts with an expansile widening of the meta-diaphysis resulting in Erlenmeyer flask deformity. The proximal and distal tibia and fibula exhibit similar lesions. Note the screw fixation of the proximal right tibia and the distal left tibia.

Case Discussion

Diaphyseal aclasis (Hereditary multiple exostoses) is an autosomal dominant disease characterized by the development of multiple osteochondromas. It can cause significant bony deformities, especially during skeletal growth as a result of the compression on the surrounding bones. Malignant transformation into chondrosarcoma may occur in 0.5-5% of the cases. Signs of malignant transformation include continuous growth after the closure of the epiphysis, cortical destruction, calcific foci especially in the cartilaginous portion of the lesion, and increased size of the cartilage cap by more than 1.5 cm.

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