Alternative to steroid therapy for myasthenia gravis and myositis occurring as immune‐related adverse events

Immunotherapy with immune checkpoint inhibitors has dramatically changed the treatment landscape for patients with cancer. Nivolumab, one of the antiprogrammed cell death-1 agents, is now the most widely used immune checkpoint inhibitor in the treatment of various advanced cancers. Programmed cell death-1 blockade leads to enhancement of the immunity against cancers in the tumor microenvironment; however, this shift in the balance of the immune system can also produce immune-related adverse events involving multiple organs. Myasthenia gravis (MG) is known to be a serious immunerelated adverse event in neuromuscular disorders that is characterized by concomitance with myositis and/or myocarditis. A neurologist in cooperation with an oncologist plays an important role in the safety management of cancer immunotherapy. We experienced a case of generalized MG and myositis occurring as immune-related adverse events that was curable without steroid therapy, only through the discontinuation of nivolumab.