What is idiopathic hypereosinophilic syndrome?

Rare illness of unknown etiology, affects multiple organ systems, result of infiltration of mature eosinophils. Peripheral eosinophilia (>1500 for 6 months) Various organ damage No parasite/ fungus/ allergy... Could be fatal if cardiac involvement (endocardial fibrosis, restrictive cardiomyopathy, valvular damage and mural thrombosis) Lung involvement 40% with dry cough and dyspnea Imaging: pulmonary edema and effusion, interstitial infiltrates (perivascular eosinophilic infiltration) Oral corticosteroid 50% response. Busulfan, interferon alpha.... used in steroid irresponsiveness.