Cardiac Troponin I and T in Checkpoint Inhibitor–associated Myositis and Myocarditis

Checkpoint inhibitor-associated myocarditis (ir-myocarditis) and myositis (ir-myositis) may occur concurrently among patients on checkpoint inhibitor immunotherapy. While cardiac-specific troponin I (cTnI) and troponin T (cTnT) are regarded to have similar sensitivities and specificities in conditions such as acute coronary syndrome, the cardiac specificity of cTnT has been challenged following observation that patients with neuromuscular diseases, including myositis, may have elevated cTnT without apparent clinical evidence of myocardial injury. Consequently, in the context of concurrent ir-myositis, cTnI may be a more appropriate biomarker for diagnosing and monitoring ir-myocarditis. To illustrate this point, we report a case of a patient with severe ir-myositis while on adjuvant programmed cell death protein 1 inhibitor immunotherapy for stage III melanoma, with accompanying elevation in cTnT.