Unmasking Eosinophilic Myocarditis: Importance of Multimodality Imaging and Histological Confirmation in a Challenging Case.

Eosinophilic myocarditis (EM) is a rare entity, characterized by a heterogeneous clinical presentation, ranging from acute heart failure to acute coronary syndrome, and associated with severe complications. Herein, we describe the case of a 78-year-old woman who presented to the ED with chest pain, elevated cardiac biomarkers, T-wave inversion on the electrocardiogram, left ventricular systolic dysfunction, and intraventricular thrombus (confirmed by contrast echo). Coronary angiography revealed the absence of obstructive coronary artery disease. Cardiac magnetic resonance (CMR) demonstrated the findings consistent with myocarditis. Due to concomitant hypereosinophilia, an endomyocardial biopsy (EB) was performed, revealing eosinophilic infiltrates. A diagnosis of EM was therefore established, and treatment with corticosteroids and anti-interleukin-5 monoclonal antibodies was initiated. This case report highlights the importance of early diagnosis of EM, a potentially elusive condition with misleading clinical features. In cases of suspected EM, CMR and, when feasible, EB are crucial to establish the diagnosis and guide appropriate therapy.