Malignant myositis ossificans: occult gastric carcinoma presenting as an acute rheumatic disorder.

A patient developed ossifying skeletal muscle metastases from a primary gastric mucin-producing adenocarcinoma. The unusual nature of skeletal muscle metastases and the inflammatory-like syndrome associated with heterotopic ossification is reviewed. It is suggested that this case of 'neoplasm-induced post-traumatic myositis ossificans' may be caused by the interaction of local haemorrhage and thrombosis, mucin-producing tumour implants, and the presence of large quantities of gamma-carboxyglutamic acid, an amino acid associated with the calcification of bone matrix formation.