[Risedronate: a possible treatment for extraosseous calcification].

A case report of 51 year-old female, diagnosed as CREST syndrome, presenting with an ectopic calcification in the left shoulder joint, which disappeared soon after the start of risedronate. She had been taking steroid and NSAIDs for the past four years, but the pain and the range of motion of her shoulder became worse and restricted progressively during the last three years only to form extraosseous calcification. Laboratory data showed normal renal function, no inflammatory changes, and no abnormalities in calcium and and phosphate metabolism including parathyroid hormone. Risedronate was administered for glucocorticoid-induced osteoporosis. Although the bone turnover markers, such as serum NTX (N-terminal telopeptides of type I collagen) and BSAP (bone specific alkaline phosphate), did not show remarkable changes, the pain disappeared a week later and the range of motion recovered a month later. The X-ray at 6 months risedronate treatment revealed a complete disappearance of the ectopic calcification. Risedronate, probably through a different process from etidronate, could prevent extraosseous calcification.