Simultaneous pembrolizumab-induced myasthenia gravis and myocarditis in a patient with metastatic bladder cancer: A case report

We report a fatal case of pembrolizumab-induced myasthenia gravis and myocarditis in a patient with metastatic bladder cancer. A 77-year-old man was aware of eye ptosis and diplopia after three weeks from first infusion of pembrolizumab, an anti-programmed cell death protein 1 monoclonal antibodies. He was diagnosed with myasthenia gravis, because he was positive on the edrophonium test and acetylcholine receptor antibody. As his echocardiography also revealed diffuse loss in wall motion with ejection fraction 29%, he was strongly suspected myocarditis. Although he was treated with prednisone and intravenous immunoglobulin, he was suddenly in cardiac arrest and passed away.