Myositis ossificans progressiva. Clinical and metabolical observations in a case treated with a diphosphonate (EHDP) and surgical removal of ectopic bone.

A 20-year-old woman with a severely crippling myositis ossificans progressiva was treated with a diphosphonate (EHDP), 10-20 mg/kg/day. While being treated with this drug, surgical removal of ectopic bone was performed. Although ectopic calcification recurred postoperatively, considerable functional improvement was achieved. At the highest dosage of EHDP, hypercalcaemia gradually appeared, but was reversible upon cessation of drug treatment. It is probably related to a direct effect of EHDP on the bone.