Hyperplastic callus formation in both femurs in osteogenesis imperfecta.

A 3-year-old boy with osteogenesis imperfecta had hyperplastic callus formation in the right femur, without preceding trauma or fracture. Radiologically, this bony mass in the femoral shaft mimicked osteosarcoma. Open biopsy showed that it was benign and suggested hyperplastic callus formation. Seven months after the biopsy, the hyperplastic callus had practically vanished. A similar process developed in the left femur 1 year later, also without fracture.