Abstract
A 54-year old patient with metastatic melanoma presented with asymptomatic myositis and myocarditis after combined immune checkpoint inhibitors (ICI) therapy (anti-programmed cell death receptor-1, anti-lymphocyte activating gene-3, and anti-indoleamine 2,3-dioxygenase-1). The diagnosis was based on the typical time window after ICI, recurrence upon re-challenge, elevations of CK, high-sensitive troponin T (hs-TnT) and I (hs-TnI), mild NT-proBNP increase, and positive magnetic resonance imaging criteria. Notably, hsTnI was found to more rapidly increase and fall and to be more heart-specific than TnT in the context of ICI-related myocarditis. This led to ICI therapy withdrawal and switch to a less effective systemic therapy. This case report highlights the differential value of hs-TnT and hs-TnI for diagnosis and monitoring of ICI-related myositis and myocarditis.