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

Abstract

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.

Keywords: clonal hypereosinophilic syndrome; eosinophilic leukemia; eosinophilic myocarditis; hypereosinophilic syndrome; intracardiac thrombus.

Figure 1. CT abdomen/pelvis with contrast showing splenomegaly (green line).

Figure 2. Four-chamber transthoracic echocardiogram showing mild left ventricular hypertrophy.

Figure 3. Phase-sensitive inversion recovery (PSIR) MRI image showing a layer of thrombus overlaying the lateral left ventricle.

Figure 4. a) Full-thickness section of the right ventricle wall including the endocardium (to left), myocardium, and epicardial fat surfaced by the mesothelium and containing a hemorrhage (to right), showing a collection of leukocytes, including numerous eosinophils at the myocardial-epicardial interface and extending into the myocardium and epicardial fat. Hematoxylin and eosin (H&E), 20x. b) Higher-magnification view of image 1 showing a collection of leukocytes, including numerous eosinophils at the myocardial-epicardial interface. H&E, 200x. c) Myocardium with eosinophils throughout the interstitium. H&E, 200x. d) Myocardium with eosinophils throughout the interstitium and focally associated with a myocyte injury (at the green arrow). H&E, 400x.