Fulminant Eosinophilic Myocarditis Without Peripheral Eosinophilia

Eosinophilic myocarditis is a rare form of myocarditis characterized by eosinophilic infiltration and usually associated with peripheral hypereosinophilia. The clinical spectrum of eosinophilic myocarditis ranges widely, from mildly symptomatic to fulminant disease. When patients have fulminant eosinophilic myocarditis, high-dose corticosteroids can lead to dramatic improvement and peripheral eosinophil counts are used as an indicator of response to treatment. However, in some patients, peripheral eosinophilia is absent at initial presentation; reaching a diagnosis and determining treatment response can be challenging in this situation. This report describes a patient with fulminant eosinophilic myocarditis who initially presented with a normal peripheral eosinophil count, was diagnosed through an early endomyocardial biopsy, and was successfully treated with corticosteroids. Endomyocardial biopsy should be performed to confirm the presence of myocardial eosinophilic infiltration, especially for patients who present with fulminant myocarditis, even when peripheral eosinophilia is absent.