Biopsy diagnosis of early myositis ossificans without radiologic evidence of calcification: success of early surgical resection.

Myositis ossificans is an uncommon disorder, which is commonly mistaken for a malignant muscle disease before histologic examination. Trauma is the most common cause of the acquired form of the disease; however, atraumatic cases have been described. The factors responsible for extraosseous ossification, such as the role of bone morphogenic protein 4, are becoming better understood. However, treatment of the disorder is not well defined. We present a case of atraumatic myositis ossificans in a 16-year-old girl that was associated with severe pain and lacked radiologic evidence of calcification. She underwent early surgical excision, resulting in immediate resolution of her symptoms. This case demonstrates that waiting for complete maturation of the lesion may not be necessary.