FIP1L1-PDGFRA Clonal Hypereosinophilic Syndrome With Eosinophilic Myocarditis and Intracardiac Thrombus

A 45-year-old man from El Salvador with no past medical history presented with cough and chest pain. Investigations revealed 60% peripheral eosinophilia (absolute count 12.3 K/uL). Cardiac imaging was consistent with myocarditis with intracardiac thrombus formation. Endomyocardial biopsy confirmed eosinophilic infiltration of the myocardium, and bone marrow biopsy showed hypercellular marrow with 28% eosinophils. Cytogenetics/fluorescence in situ hybridization (FISH) confirmed positive FIP1L1-PDGFRA rearrangement. The patient was treated for FIP1L1-PDGFRA clonal hypereosinophilic syndrome with associated eosinophilic myocarditis and intracardiac thrombus. The treatment regimen consisted of a steroid taper, imatinib, and anticoagulation. Treatment was followed by normalization of the eosinophil count. At two-year follow-up, the patient was without recurrence of eosinophilia on maintenance imatinib and indefinite anticoagulation with warfarin.