SHM Converge Scientific Abstract ePoster Gallery-A Trio of Trouble: A Case of Pembrolizumab-Induced Triple M Syndrome

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This case report describes a 79-year-old man with stage IIIb melanoma treated with pembrolizumab who developed immune checkpoint inhibitor–induced “Triple M syndrome,” an overlap syndrome involving myocarditis, myositis, and myasthenia gravis. After his second dose of pembrolizumab, he presented with worsening bulbar symptoms, dyspnea, bilateral complete ophthalmoplegia, and lower-extremity weakness.<br /><br />Workup showed severe muscle and cardiac injury, including creatine kinase of 5,380 U/L and troponin elevation to 1,718 ng/L. EMG suggested a myopathic process, and anti-striated muscle antibodies were positive. Although EKG and echocardiogram were normal, the clinical picture supported Triple M syndrome.<br /><br />Treatment began with IV methylprednisolone and pyridostigmine, but his condition worsened and he required intubation on hospital day 3 due to progressive diaphragmatic weakness. Immunosuppression was escalated to plasmapheresis followed by IVIG. On day 14, additional therapy with ruxolitinib and abatacept was started. He later received five more abatacept infusions, each associated with troponin decreases after prior elevations. Over time, his strength, eye movements, and troponin levels improved, and he was discharged to inpatient rehabilitation with a long-term ventilator weaning plan.<br /><br />The report emphasizes that Triple M syndrome is rare but high risk, with estimated incidence around 1% and in-hospital mortality near 40%. Because symptoms may overlap and be missed, early recognition and rapid multidisciplinary management are critical. It also highlights that many cases are steroid-refractory and need prompt escalation to additional immunosuppressive therapies.

Asset Subtitle

Amrit K. Bhandal

Meta Tag

Author List Amrit K. Bhandal, Emily Marquet, Mildred Hernandez Sanchez

Category Clinical Vignettes

Concept Triple M Syndrome

Concept Myocarditis

Concept Myositis

Concept Myasthenia Gravis

Concept Immune Checkpoint Inhibitor

Distinguished Non-Finalist

Presenter Organization UC Davis School of Medicine

Presenting Author Amrit K. Bhandal

Track Adult

Keywords

pembrolizumab

Triple M syndrome

immune checkpoint inhibitor

myocarditis

myositis

myasthenia gravis

melanoma

plasmapheresis

IVIG

abatacept

Triple M Syndrome

Myocarditis

Myositis

Myasthenia Gravis

Immune Checkpoint Inhibitor