Background: The high-sensitive cardiac troponin T (hs-cTnT, Elecsys^®) is an excellent and worldwide used diagnostic marker for myocardial ischemia with high sensitivity. However, elevated hs-cTnT levels are found in different systemic diseases and can lead to misdiagnosis. The high-sensitive cardiac troponin I (hs-cTnI, ARCHITECT^®) shows comparable sensitivity. However, hs-cTnI is much more specific than hs-cTnT (92% vs. 80%, 99th percentile). Case summary: An asymptomatic women with a cancer of unknown primary (CUP) presented constantly high hs-cTnT. Electrocardiogram, echocardiography as well as cardiac MRI and CT angiography of the coronary arteries showed no pathological findings. Accordingly, the measurement of the more specific hs-cTnI showed no significant increase. A repeated clinical examination revealed a localized scleroderma and autoimmune antibody pattern diagnosed a paraneoplastic systemic sclerosis (SSc). Therefore, a treatment with Rituximab — a CD20 antibody — was initiated, which reduced activity of SSc and also concentration of hs-cTnT. Conclusion: In the present case, a localized scleroderma due a paraneoplastic SSc was accompanied by elevated hs-cTnT levels in the absence of cardiovascular disease. A reduced inflammation of skeletal muscle tissue due to rituximab treatment decreased hs-cTnT levels. This is the first report of an occult hs-cTnT elevation due to paraneoplastic SSc.