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Case Reports
. 2025 Jun;17(8):561-566.
doi: 10.1080/1750743X.2025.2517522. Epub 2025 Jun 13.

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

Stephanie S Cobelas-Cartagena  1 , Emilio Amigo-Otero  2 , Victoria García-Samblas  1 , Jesus Flores-Raposo  1 , Silvia Rodrigo-Herrero  3 , Juan Bayo-Calero  1
Affiliations
Case Reports

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

Stephanie S Cobelas-Cartagena et al. Immunotherapy. 2025 Jun.

Abstract

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).

Keywords: Efgartigimod; Immune checkpoint inhibitors; case report; immune-related adverse events; myocarditis, myositis and myasthenia gravis overlap syndrome (IM3OS).

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Conflict of interest statement

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.

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