Severe Myocarditis after nivolumab and ipilimumab in a patient with microsatellite instability‑high gastric adenocarcinoma: A Case Report

Abstract

Myocarditis attributable to immune checkpoint inhibitors is regarded as among the most serious complications of immunotherapeutic treatment. We report a case of gastric cancer who developed myocarditis, and subsequent late complications following treatment with nivolumab and ipilimumab. The patient was managed with corticosteroids, mycophenolate mofetil (MMF), and intravenous immunoglobulin G (IVIG), but later developed supraventricular tachycardia and deep vein thrombosis. This report emphasizes the need to enhance recognition of immune‑related toxicities within non‑oncology specialties to support prompt interdisciplinary collaboration and appropriate patient management. Additionally, patients can develop myocarditis‑related complications even when clinically stable or near the end of treatment, underscoring the need for close and ongoing monitoring.