Immune checkpoint inhibitor-induced myopericarditis.

A woman in her 30s with a medical history of metastatic rectal adenocarcinoma, currently on pembrolizumab, which started a few weeks ago, was admitted for abdominal pain. During the hospital stay, she experienced sharp chest pain. Troponin was 1885 ng/mL which peaked at 7338 ng/mL. ECG was unremarkable. The echocardiogram showed an Ejection fraction (EF) of 55%-60% and basal-inferior wall hypokinesis. Left heart catheterisation showed no coronary abnormalities. Cardiac MRI showed a non-coronary area of focal T1 and T2 hyperintense signal and transmural delayed gadolinium enhancement in the mid-basal inferior/inferoseptal wall consistent with myocardial damage. Pericardium showed increased thickness and adhesions at the right ventricular outflow tract consistent with pericarditis. Steroid therapy was initiated, and a marked clinical response was achieved. Immune checkpoint inhibitor-induced myocarditis and pericarditis is a rare complication associated with a high mortality rate, if untreated. Diagnosis requires a multidisciplinary approach, and early detection is critical to preventing a fatal outcome.