Myasthenia gravis and myopathy after nivolumab treatment for non‐small cell lung carcinoma: A case report

Here, we report a case of myasthenia gravis and myopathy in a patient treated with nivolumab. A 76‐year‐old man who had been treated with four doses of nivolumab because of non‐small cell lung cancer (NSCLC) presented with proximal‐dominant muscle weakness and fluctuating ptosis and diplopia. Serologic studies revealed increased levels of muscle enzymes including creatine phosphokinase (2934 U/L), and acetylcholine receptor antibody was positive (1.31 nmol/L). Following electrodiagnostic study, he was diagnosed with myasthenia gravis and active stage of myopathy. After discontinuation of nivolumab, he was treated with corticosteroids, intravenous immunoglobulin G, and pyridostigmine. The neuromuscular symptoms and serologic abnormalities of the patient markedly improved. Currently, he is taking oral steroids and pyridostigmine without further immunotherapy.