Severe mitral valve involvement in a child with hypereosinophilia secondary to parasitic infection.

An 11-year-old boy with severe mitral regurgitation due to hypereosinophilia caused by infection with a filaria (Mansonella perstans) required mitral valve replacement with a prosthetic valve. During recurrent postoperative hypereosinophilia, the patient experienced severe mitral stenosis due to thrombosis of the mitral prosthesis. Despite adequate anticoagulation, the prosthesis had to be replaced as an emergency with a second prosthetic valve. Permanent control of the eosinophil count was achieved with chronic oral steroid administration. In contrast to other microfilariae, M. perstans is non-pathogenic to humans; nevertheless, longstanding hypereosinophilia may lead to severe cardiac involvement endangering the patient's life.