Abstract Background Epigastric or chest pain with an abnormal electrocardiogram (ECG) in a young, otherwise healthy patient should trigger an investigation to rule out myocarditis. The myocarditis covers a wide spectrum of severity. The search for the aetiologic factor could be definitive for the success of therapy. Case summary A previously healthy 29-year-old woman presented to the Emergency Room with epigastric pain, eosinophilia, and an abnormal ECG. A thorough evaluation including cardiac magnetic resonance and endomyocardial biopsy was undertaken. A diagnosis of acute necrotizing eosinophilic myocarditis was made. Discussion The case is particularly unique for its suspected predisposing trigger: an antimigraine drug. A possible systemic hypersensitivity reaction, reflected by the occurrence of concomitant severe serum eosinophilia, acute myocarditis, and central nervous system vasculitis, was successfully treated with steroids, further supporting the diagnosis.