SHM Converge Scientific Abstract ePoster Gallery-Pembrolizumab-Induced Triple M Syndrome in a Patient With Stage Iii Melanoma: A Case Report

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This case report describes a rare and fatal immune-related toxicity from pembrolizumab, a checkpoint inhibitor used to treat stage III melanoma. A 70-year-old man developed the “triple M syndrome” overlap of myocarditis, myositis, and myasthenia gravis (IM3OS), a serious but uncommon complication of immune checkpoint inhibitor therapy.<br /><br />He presented with diplopia and ptosis, and testing revealed markedly elevated cardiac and muscle injury markers, including troponin, creatine kinase, and aldolase. Autoantibody testing showed positive acetylcholine receptor binding antibody, supporting myasthenia gravis. His electrocardiogram showed complete heart block, requiring pacemaker placement, and immune-mediated myocarditis was suspected.<br /><br />Treatment was initiated with high-dose methylprednisolone and abatacept, which improved weakness somewhat, but muscle enzymes remained elevated. He was then transferred for further care, where he received intravenous immunoglobulin (IVIG) and ruxolitinib. Despite these interventions, he later developed recurrent ventricular arrhythmias and died.<br /><br />The report emphasizes that overlap syndrome involving myocarditis, myositis, and myasthenia gravis is rare, but can progress rapidly and carry high mortality, especially when myocarditis is involved. Early recognition and prompt treatment with corticosteroids, IVIG, and possibly plasmapheresis may improve outcomes. The authors suggest that delay in starting IVIG may have contributed to the poor outcome in this case. They call for greater awareness, close monitoring, and further research into immune-related adverse events from pembrolizumab and other checkpoint inhibitors.

Asset Subtitle

Santiago Imhoff

Meta Tag

Author List Kemar O. Barrett, Maxwel Janosky, Natasha Rastogi, Santiago Imhoff

Category Clinical Vignettes

Concept Immune Checkpoint Inhibitor

Concept Immune-Related Adverse Event

Concept Myocarditis

Concept Myositis

Concept Myasthenia Gravis

Distinguished Non-Finalist

Presenter Organization Hackensack University Medical Center/ Englewood Hospital

Presenting Author Santiago Imhoff

Track Adult

Keywords

pembrolizumab

immune checkpoint inhibitor

myocarditis

myositis

myasthenia gravis

triple M syndrome

IM3OS

melanoma

cardiotoxicity

immune-related adverse events

Immune Checkpoint Inhibitor

Immune-Related Adverse Event

Myocarditis

Myositis

Myasthenia Gravis