Acute Myocarditis Initially Presenting as Inflammatory Gastroenteritis With a Delayed Onset of Typical Chest Pain: A Diagnostic Challenge

Acute myocarditis is an inflammatory disease of the myocardium with highly variable clinical presentations. While chest pain and dyspnea are common, atypical extracardiac manifestations may delay diagnosis, particularly in the absence of electrocardiographic abnormalities. Cardiac magnetic resonance imaging (CMR) has become the cornerstone for noninvasive diagnosis using the revised Lake Louise criteria. A 37-year-old male presented with acute abdominal pain, inflammatory watery diarrhea, nausea, vomiting, and fever following recent food intake. Initial evaluation supported infectious gastroenteritis, including elevated fecal leukocytes and inflammatory markers. Shortly after admission, the patient developed chest discomfort, which prompted further cardiac investigation. Electrocardiography and echocardiography were normal. Serial high-sensitivity troponin-T levels subsequently demonstrated progressive elevation. CMR revealed myocardial edema and subepicardial late gadolinium enhancement involving the lateral and inferior walls, consistent with acute myocarditis. Typical inflammatory chest pain became more evident later in the clinical course. The patient was treated conservatively and discharged in stable condition. This case highlights that myocarditis may initially mimic gastrointestinal disease. The emergence of chest discomfort or progressive troponin elevation should prompt further cardiac evaluation, even in the absence of early ECG abnormalities. Early use of CMR is essential for diagnosis in atypical presentations.