Tocilizumab in immune checkpoint inhibitor-induced myositis, myocarditis, and myasthenic syndrome: a rare case report and review of the literature.

Immune-related adverse events (irAEs) associated with immune checkpoint inhibitors (ICI) are becoming more frequent with the growing use of these agents in routine clinical oncology. This mechanism enhances the anti-tumor immune response, increasing the risk of activating autoreactive T cells, and leading to immune-mediated manifestations. The spectrum of these manifestations is widely variable. ICI-associated myositis is among the most severe irAEs, being a rare but serious complication with significant morbidity and mortality, particularly when accompanied by myocarditis and/or myasthenic crisis, which can all occur concurrently and worsen clinical outcomes. We report the case of a 78-years-old man with metastatic colon adenocarcinoma who developed ICI-associated myositis with concomitant myocarditis and myasthenic syndrome. In the presented case, the use of tocilizumab, an anti-interleukin 6 (IL-6)-receptor monoclonal antibody, was effective in treating the myositis and myocarditis, but not the myasthenic component of this ICI-associated myositis.