Invasive ductal breast cancer associated polymyositis causing respiratory failure

Polymyositis (PM) is a very rare paraneoplastic syndrome in association with breast cancer, here we present a breast cancer patient with a sudden onset of respiratory failure caused by PM. A 47-year-old woman, with a history of a lump in her right breast for 3 months, weakness and anorexia for about 1 month, suddenly presented with respiratory failure and elevated muscle enzymes. Muscle biopsy revealed myositis and breast biopsy was consistent with invasive ductal breast cancer. Decreases of muscle enzyme levels were observed after corticosteroid therapy and the lumpectomy, but the patient died from respiratory failure. A case of respiratory failure caused by breast cancer associated polymyositis was presented. This case server to remind that breast cancer patients with muscle weakness or muscle enzyme elevation may be involved with PM.