From bone marrow to the heart: a case report of cardiac involvement in myeloproliferative-associated hypereosinophilic syndrome.

A 36-year-old man with marked eosinophilia presented with fatigue and dyspnea. Echocardiography revealed biventricular apical thickening and thrombi, confirmed by contrast imaging. Cardiac magnetic resonance demonstrated global systolic dysfunction,myocardial edema, and subendocardial late gadolinium enhancement, consistent with early-thrombotic-stage Loeffler endocarditis. Bone marrow biopsy identified a FIP1L1-PDGFRA fusion, confirming myeloproliferative hypereosinophilic syndrome. High-dose corticosteroids followed by imatinib induced hematologic and cardiac improvement, with complete thrombus resolution at follow-up. Τhis case illustrates that the integration of advanced multimodal imaging with targeted genetic analysis can reliably establish the diagnosis of Loeffler endocarditis, obviating the need for invasive histopathological confirmation in appropriately selected patients.