SHM Converge Scientific Abstract ePoster Gallery-Pembrolizumab-Induced Myositis and Myocarditis Presenting as Ptosis and Diplopia

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A 78-year-old man with a history of multiple cancers, including scalp melanoma, presented less than a week after pembrolizumab infusion and influenza vaccination with bilateral ptosis, diplopia, myalgias, and proximal leg weakness. He was initially evaluated for immune checkpoint inhibitor (ICI)-induced myositis, with myasthenia gravis and neuropathy also considered.<br /><br />Testing showed markedly elevated creatine kinase (3224) and troponin (1237). Electromyography demonstrated a diffuse myopathic process involving the cranial muscles. Extensive autoimmune, neuromuscular, and paraneoplastic workup was negative. Brain MRI showed no recurrence or metastasis. PET scan revealed multifocal intramuscular FDG uptake suggesting myositis. Although echocardiography was normal, cardiac MRI showed findings consistent with acute myocarditis, confirming concurrent ICI-induced myositis and myocarditis.<br /><br />Because of concern for severe immune-related toxicity, pembrolizumab was stopped and the patient was admitted for monitoring. He was treated with high-dose IV methylprednisolone, 1 g daily for 5 days, along with prophylaxis for Pneumocystis jirovecii pneumonia, gastrointestinal protection, and calcium/vitamin D supplementation. His CK and troponin levels improved during hospitalization. He was discharged on prednisone 2 mg/kg/day with close follow-up in an ICI toxicity clinic.<br /><br />The report emphasizes that immune checkpoint inhibitors can cause rare but life-threatening adverse events such as myositis and myocarditis. Sudden symptoms after ICI exposure should prompt immediate lab evaluation, imaging, and early treatment with steroid therapy, since rapid recognition and management can prevent serious complications.

Asset Subtitle

Sayeh Fattahi

Meta Tag

Author List Meltiady Issa, Sayeh Fattahi

Category Clinical Vignettes

Concept Immune Checkpoint Inhibitor Toxicity

Concept Myositis

Concept Myocarditis

Concept Corticosteroid

Concept Muscle Weakness

Distinguished Non-Finalist

Presenter Organization Mayo Clinic Alix School of Medicine

Presenting Author Sayeh Fattahi

Track Adult

Keywords

pembrolizumab

immune checkpoint inhibitor

myositis

myocarditis

ptosis

diplopia

creatine kinase

troponin

methylprednisolone

influenza vaccination

Immune Checkpoint Inhibitor Toxicity

Myositis

Myocarditis

Corticosteroid

Muscle Weakness