Abstract
A 34-year-old man presented with fever, palpitations, maculopapular rash, pharyngitis, left cheilitis, and bilateral gonalgia. High-sensitivity troponin I concentration was 4,900 ng/l. Transthoracic echocardiogram revealed reduced global longitudinal strain. Cardiac magnetic resonance imaging showed acute myocarditis. Adult-onset Still's disease was diagnosed, and treatment with intravenous corticosteroids and tocilizumab was initiated. (Level of Difficulty: Beginner.).