A case report of nivolumab-induced myasthenia gravis and myositis in a metastatic renal cell carcinoma patient.

We present a 78-year-old male with renal cell carcinoma who developed myasthenia gravis complicated by myositis after nivolumab administration, which was verified by the presence of antibodies against the acetylcholine receptor. The initial symptom was posterior neck pain, and biochemical examination of blood showed elevated levels of hepatic enzymes and creatine phosphokinase. The level of antibody against the acetylcholine receptor increased 4.1-fold. His condition progressed rapidly resulting in respiratory failure 15 days after conservative therapy.