Immune-related adverse event-myocarditis with marked ST-segment elevation requiring differentiation from COVID-19-induced myocarditis: a case report

Background Immunotherapy with immune checkpoint inhibitors (ICIs) enhances the host immune reaction against tumour cells by inhibiting intrinsic down-regulators of the T cell-mediated immune response. Although the advent of ICIs has dramatically changed oncology, ICIs may also trigger an overactivation of T cells against non-cancerous tissues, leading to off-target immune-related adverse events (irAEs). Case summary A 64-year-old man with a history of seven courses of atezolizumab, an ICI, for small-cell lung cancer and coronavirus disease 2019 (COVID-19) was admitted to the hospital complaining of acute chest pain. Transthoracic echocardiography showed preserved ejection fraction (EF), but electrocardiography indicated precordial ST-elevations and marked increases in biomarkers for myocardial injury were observed. Emergent cardiac catheterization showed no significant coronary stenosis. On the fifth hospital day, EF decreased to 25% and pericardial effusion occurred. Endomyocardial biopsy was immediately performed, and prednisolone (60 mg/day) was administered. Troponin I level rapidly reduced, ST changed, and EF improved. Histological examinations demonstrated CD8-predominant T lymphocytic infiltration with myocardial cell injury, consistent with irAE-myocarditis. Discussion In irAEs, myocarditis is the most common and severe cardiac manifestation with a high mortality. Even at 20 weeks after the initial ICI treatment, irAE-myocarditis occurs and the clinical presentation may mimic ST-elevation myocardial infarction. The histopathological findings suggested the high possibility of irAE-myocarditis rather than COVID-19-induced myocarditis, but COVID-19 has possibly played a role in the development of late-onset irAE-myocarditis. This educational case implies the importance of immediate recognition of irAE even after stable ICI treatment.