Myositis associated with interleukin‐2 therapy in a patient with metastatic renal cell carcinoma

Background. Interleukin‐2 (IL‐2) has been used successfully in the treatment of some patients with metastatic renal cell carcinoma and melanoma, with a partial response rate of 15%–20%. It produces a well documented spectrum of side effects. Autoimmune diseases have been associated with IL‐2 immunotherapy and the development of autoimmune thyroiditis may correlate with anti‐tumor clinical response. Methods. A patient with metastatic renal cell carcinoma is described who developed a polymyositis‐like myopathy after an autologous tumor vaccine and IL‐2 therapy. Results. The patient had a delayed response for 15 months after developing this previously unreported toxicity. Conclusions. To the authors' knowledge, this represents the first reported case of necrotizing myositis in association with IL‐2 therapy. Subsequent continuous partial response of the advanced malignancy was observed for 15 months. In this case, IL‐2 may have broken tolerance to both normal muscle cells and tumor cells.