Early‐Stage Loeffler's Endocarditis with Isolated Right Ventricular Involvement: Management, Long‐Term Follow‐Up, and Review of Literature

Loeffler's endocarditis is a clinical condition characterized by combination of three key findings: unexplained prolonged and marked eosinophilia (>1500 eosinophils/mm 3 ), absence of a primary cause of hypereosinophilia, and evidence of eosinophil‐mediated organ damage. We report a case of a 55‐year‐old African American male with symptoms of heart failure. Hematology showed white blood cell count of 17 670/mm 3 with 63% eosinophils and an absolute eosinophil count of 11 133/mm 3 . Echocardiogram and computed tomography showed near complete obliteration of right ventricular cavity. Endomyocardial biopsy showed diffuse myocyte necrosis with extensive eosinophilic infiltration without fibrosis consistent with early Loeffler's endocarditis. Molecular and cytogenetic analyses of bone marrow cells were negative for FIP 1L1‐ PDGFRA fusion, PDGFRB mutation, abnormal myeloid maturation, or a lymphoproliferative disorder. Flow cytometry showed no clonality excluding chronic eosinophilic leukemia. There was a complete resolution of symptoms and eosinophilia after 1 month of steroid therapy.