Pembrolizumab and Enfortumab-Induced Immunotherapy Myocarditis

A 64-year-old male with coronary artery disease, hypertension, hyperlipidemia, obstructive sleep apnea, and right ureteral urothelial carcinoma presented with chest pain, neck weakness, and myalgias after his first cycle of pembrolizumab and enfortumab vedotin. He developed a non-ST-segment elevation myocardial infarction (NSTEMI) alongside suspected immune checkpoint inhibitor (ICI)-associated myocarditis and myositis. Initial tests showed elevated troponin at 568 ng/L, creatinine phosphokinase (CPK) at 3,332 U/L, and transaminases. ECG revealed anterolateral ST-segment depression and left anterior fascicular block. Cardiac catheterization confirmed 90% mid-left anterior descending (LAD) artery stenosis, treated with a drug-eluting stent, and endomyocardial biopsy verified focal moderate lymphocytic myocarditis with myocyte necrosis. Treatment with high-dose methylprednisolone and intravenous immunoglobulin led to improvement in symptoms, biomarkers, and cardiac function. He was discharged on prednisone taper, dual antiplatelet therapy, anticoagulation, and prophylaxis, with outpatient follow-up arranged.