Abstract
Background: Immune checkpoint inhibitor (ICI)-related myocarditis is a rare adverse effect of ICI's. When accompanied by overlapping myasthenia gravis, prognosis is worsened. While established guidelines aid in the treatment of ICI-associated adverse events, management of overlapping syndromes is complex and challenging. Case description: A 66-year-old man with metastatic renal cell carcinoma recently started on ipilimumab and nivolumab presented with dizziness and diplopia. He had high-grade atrioventricular (AV) block with junctional escape. He had elevated troponin, transaminases, and creatinine kinase. Coronary angiogram showed no evidence of obstructive coronary artery disease. A permanent pacemaker was placed. Cardiac MRI showed no specific features of myocarditis, though quality was limited by pacemaker artifact; left ventricular ejection fraction was 29%. MRI of the orbits showed no signs of extraocular myositis. Acetylcholine receptor (AChR) antibody and muscle-specific kinase (MuSK) antibody was negative. Given ongoing suspicion for ICI-associated adverse events, the patient underwent endomyocardial biopsy. This revealed lymphocytic myocarditis, confirming the diagnosis of ICI-related myocarditis. Despite improvement of troponin, transminases, and creatinine kinase, he developed progressive weakness, dysphagia, and respiratory failure, and died one month after initial presentation. Discussion: We highlight a case of ICI-related myocarditis presenting as high-grade AV block with concurrent hepatitis, myositis, and probable serologic-negative myasthenia gravis (MG). Overlapping syndromes are common in patients with exposure to ICI's, and are associated with significantly higher mortality. Although steroids are first-line for treating ICI-associated adverse events including myocarditis, they can initially lead to acute worsening of MG symptoms. While our patient had laboratory and biomarker improvement of his myocarditis, hepatitis, and myositis, he developed progressive weakness and respiratory failure. Our case highlights the complexity and challenges of managing ICI-related myocarditis and overlapping syndromes, including MG, and its poor prognosis despite prompt treatment.
Published Version
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