Organ-Restricted Hypereosinophilic Syndrome

Eosinophilic myocarditis (EM) is a rare inflammatory condition that is characterized by eosinophilic myocardial infiltration. We present a case of hypereosinophilic syndrome (HES) presenting as EM, complicated by cardiac tamponade. A 22-year-old man with a history of asthma presented with hypotension and chest pain. Work-up revealed myopericarditis with tamponade, eosinophil-rich pericardial effusion, and infection with influenza A. Despite initial improvement, he had recurrent episodes with elevated troponin, eosinophilia, and reduced left ventricular ejection fraction. Extensive work-up excluded malignancy and revealed biopsy-confirmed EM suggestive of HES. He responded to corticosteroids and was managed with guideline-directed heart failure medications. Cardiac involvement as the initial presentation of HES is uncommon and represents a major contributor to morbidity and mortality. In patients presenting with acute heart failure and cardiac tamponade of uncertain etiology, a diagnostic work-up for EM should be initiated regardless of the presence of hypereosinophilia on the peripheral blood smear.