[Permanent constriction of the jaws due to progressive ossifying myositis]

A case is reported of progressive ossifying myositis (fibrodysplasia ossificans progressiva, Münchmeyer's disease) with onset at 16 years of age by a lesion of internal pterygoid with limitation of opening of mouth. Surgery to relieve ankylosis was followed by recurrence. Diagnosis was established only after the appearance of lesions in other regions (sternocleidomastoid, latissimus dorsi, lumbar muscles...). Clinical and paraclinical signs of this exceptionally rare disease are reviewed and diagnostic difficulties at onset of the disease discussed. Treatment of acute myositis episodes with diphosphonates delays passage to the ossification stage, allowing local surgery to be performed with less risk of relapse.