Mitral valve replacement in idiopathic hypereosinophilic syndrome.

Idiopathic hypereosinophilic syndrome is a rare systemic disease that can cause one form of endocardial fibrosis. Endocardial fibrous tissue with overlying thrombus formation in idiopathic hypereosinophilic syndrome leads to a restrictive cardiomyopathy that may produce mitral and/or tricuspid regurgitation. This report describes a patient with idiopathic hypereosinophilic syndrome who underwent mitral valve replacement and successful steroid therapy for an usually localized form of endocardial fibrosis.