Value of troponin T versus I in the diagnosis of immune checkpoint inhibitor‐related myocarditis and myositis: rechallenge?

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.