The clinical chameleon: eosinophilic myocarditis presenting as acute coronary syndrome—a case report

Eosinophilic myocarditis is a rare inflammatory cardiomyopathy that may clinically mimic acute coronary syndrome and should be considered in patients with non-obstructive coronary arteries, often resulting in diagnostic delay.

A 27-year-old man presented with recurrent chest pain and was initially misdiagnosed with a panic attack. On admission, laboratory evaluation revealed marked peripheral eosinophilia (1800/mm³), mildly elevated troponin, and increased serum IgE levels. Echocardiography demonstrated reduced left ventricular ejection fraction and a large apical intracavitary thrombus. Coronary angiography revealed normal coronary arteries. Cardiac magnetic resonance imaging showed myocardial oedema and circumferential subendocardial late gadolinium enhancement consistent with eosinophilic myocarditis. Extensive aetiological workup was negative. Although endomyocardial biopsy showed non-specific findings, the diagnosis was established through multimodal integration of clinical, imaging, and laboratory data. High-dose corticosteroid therapy and anticoagulation resulted in rapid clinical improvement, recovery of ventricular function, and near-complete thrombus resolution.

Eosinophilic myocarditis should be considered in young patients presenting with chest pain and non-obstructive coronary arteries. Multimodality imaging—particularly cardiac magnetic resonance—plays a key role in diagnosis, while early corticosteroid therapy may lead to rapid clinical and functional recovery.

This case underscores the importance of maintaining a high index of clinical suspicion for EM in young patients presenting with chest pain and peripheral eosinophilia. A multimodal diagnostic approach integrating cMRI findings, laboratory data, and exclusion of alternative aetiologies is essential when biopsy results are inconclusive. Early immunosuppressive therapy is key to reversing myocardial damage and preventing progression to end-stage heart failure.