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MG-Myositis-Myocarditis Overlap — SCE Medical Oncology MCQ

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HardOncological EmergenciesMG-Myositis-Myocarditis OverlapSCE Medical Oncology

A 58-year-old woman on ipilimumab + nivolumab for melanoma develops new diplopia, ptosis, dysphagia and proximal weakness. Anti-striated muscle antibodies are positive. CK is 8,000 IU/L. Troponin is 500 ng/L. What is this syndrome and why is it a medical emergency?

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Correct answer: A — Myasthenia gravis-myositis-myocarditis overlap syndrome — a rare but potentially fatal triad requiring immediate ICU admission, ICI discontinuation, high-dose IV methylprednisolone and possible IVIG/plasmapheresis

The ICI-related myasthenia gravis-myositis-myocarditis overlap syndrome is one of the most lethal irAEs (mortality 30-50%). It presents with bulbar symptoms (dysphagia, ptosis, diplopia), proximal weakness, CK elevation (myositis) and troponin elevation (myocarditis). Anti-striated muscle antibodies are often positive. Management requires: immediate ICI cessation, ICU admission (respiratory monitoring — myasthenic crisis risk), IV methylprednisolone 1 g/day × 3-5 days, and early IVIG or plasmapheresis. Cardiac monitoring is essential.

Reference: ESMO 2024 irAE Management; Guidon et al JAMA Neurol 2021; Anquetil et al Medicine 2018