Hypereosinophilic endocarditis presenting with intracardiac mass and severe mitral regurgitation: a case report of FIP1L1-PDGFRA positive myeloid neoplasm.

Loeffler's endocarditis is a serious manifestation of hypereosinophilia, and it is associated with endomyocardial fibrosis, thrombus formation, valvular dysfunction, and, rarely, intracardiac mass lesions. A 28-year-old male patient had progressive dyspnoea, facial oedema, and fatigue for 2 years. A 2D trans-thoracic echocardiogram revealed a 24 × 15 mm mobile echogenic mass attached to the mitral valve, associated with severe mitral regurgitation. Blood counts showed hypereosinophilia. Cardiac MRI showed subendocardial fibrosis. Bone marrow examination showed increased hypercellularity, and molecular testing was positive for FIP1L1-PDGFRA fusion, confirming a myeloid neoplasm with hypereosinophilia. The patient was treated with corticosteroids, anticoagulation, and Imatinib. Following initiation of therapy, the mass size reduced, and the patient improved symptomatically. This case emphasizes the importance of a thorough diagnostic workup, including genetic testing in Loeffler's Syndrome, to guide therapy. Recognizing molecularly driven eosinophilic disorders is essential, as targeted treatment can significantly improve prognosis. The presence of the Fip1-Like1-platelet-derived growth factor receptor alpha (FIP1L1-PDGFRα) fusion gene is a rare cause of hypereosinophilic syndrome requiring a distinct therapeutic approach.