A Rare Case of Isolated Right Ventricular Loeffler's Endocarditis in Primary Hypereosinophilic Syndrome.

Hypereosinophilic syndrome (HES) is a systemic disorder with various manifestations, characterized by hypereosinophilia and caused by primary or secondary conditions. Loeffler's endocarditis (LE) represents a frequent cardiac manifestation of HES, caused by infiltration of the myocardium by eosinophilic cells, which determines endocardial damage, with subsequent inflammation, thrombosis, and fibrosis of either one or both ventricles. The diagnosis of cardiac involvement is based on a multimodality approach (i.e., two-dimensional transthoracic echocardiography [2D-TTE], speckle-tracking echocardiography [STE], and cardiac magnetic resonance [CMR]), with different findings depending on the stage of disease. STE may be useful in the initial phase when traditional imaging techniques may result negative, whereas CMR allows myocardial tissue characterization along with a better definition of the right ventricle. We present a rare case of LE with isolated right ventricular involvement in a patient with HES caused by chronic eosinophilic leukemia with constitutively activated fusion tyrosine kinase on chromosome 4q12, successfully treated with imatinib mesylate.