alpha-Interferon treatment for idiopathic hypereosinophilic syndrome.

Idiopathic hypereosinophilic syndrome (HES) is a poorly understood disorder characterized by a markedly elevated peripheral blood eosinophil count in the absence of known associated causes of hypereosinophilia. Idiopathic hypereosinophilic syndrome is associated with eosinophil-induced organ damage, including endomyocardial and pulmonary fibrosis, stroke, and gastrointestinal disease. Treatment of idiopathic HES is centered on the reduction of peripheral circulating eosinophils in an effort to diminish tissue infiltration and destruction. Multiple cytotoxic agents have been tried, with variable results. Prednisone and hydroxyurea have remained the therapies of choice in long term treatment of idiopathic HES. We report here the successful 2 year treatment of aggressive idiopathic HES, refractory to hydroxyurea and prednisone, with alpha-interferon.