[A case of polymyositis associated with transverse colon cancer that responded to tumor resection and chemotherapy].

A 72-year-old woman was admitted to our hospital because of muscle weakness and was diagnosed as having polymyositis. Whole-body evaluation revealed advanced transverse colon cancer, and we therefore considered it likely that the patient had paraneoplastic myositis. We performed a curative surgical resection for colon cancer, after which her serum creatine phosphokinase(CPK)level greatly decreased. Steroid therapy was administered postoperatively. However, her CPK levels remained persistently high, even after steroid pulse therapy, and we considered that this was due to steroid-resistance myositis. We administered chemotherapy for colon cancer using 5-fluorouracil plus Leucovorin(5-FU/LV), after which the CPK levels gradually decreased. There have been few previous reports of polymyositis associated with colon cancer and a standard treatment for paraneoplastic myositis has not been established. Most clinicians believe that treatment of the primary tumor may contribute to an improvement of myositis, and in our case, tumor resection and chemotherapy were effective.