The first case of polymyositis associated with interferon therapy

A 54-year-old man with renal cell carcinoma was treated with interferon (IFN)-gamma for 3 weeks soon after nephrectomy. Three months later he received IFN-alpha therapy for 8 weeks due to chronic active hepatitis C. He subsequently contracted polymyositis (PM): proximal muscle weakness, an elevation of muscle enzymes, myogenic patterns on the electromyograph and histologically specific findings in biopsied muscle specimens. After discontinuation of IFN his muscular weakness gradually recovered.