Hypereosinophilic syndrome with extensive myocardial involvement and mitral valve thrombus instead of mural thrombi.

A 68-year-old woman complained of repeated signs of congestive heart failure during the last 10 years. Clinical examination revealed persistent marked eosinophilia of the peripheral blood. Postmortem examination of the heart revealed multiple thrombo-embolic materials of the small vascular lumina throughout the myocardium, associated with marked perivascular and stromal infiltration of eosinophils, many foci of myocardial necrosis, and diffuse myocardial fibrosis. There was also an organizing thrombus in the posterior mitral valve. Neither subendocardial fibrosis, overlying mural thrombi in the endocardium, pulmonary infiltration of eosinophils nor systemic granulomatous or healed vasculitis in the lungs and other organs were found. The disease is preferably consistent with a diagnosis of hypereosinophilic syndrome of Hardy et al., a group of ill-defined and overlapping conditions, and best descriptively termed as eosinophilic interstitial myocarditis.