Pembrolizumab-induced myocarditis, myositis, and myasthenia gravis overlap syndrome (IM3OS) treated with Efgartigimod: case report.

The use of immune checkpoint inhibitors (ICIs) has revolutionized the treatment of many malignancies. However, they may be associated with life-threatening immune-mediated adverse effects.In this article, we present the case of a patient diagnosed with stage IIB acral melanoma (pT4aN0M0) who started adjuvant treatment with pembrolizumab, after which he developed severe myocarditis with myositis and myasthenia gravis overlap syndrome (IM3OS) treated with Efgartigimod.The use of Efgartigimod resulted in a remarkable recovery, marking the first reported acute application of this agent for IM3OS and positive anti-acetylcholine receptor antibodies (anti-AChR).