Treatment of idiopathic hypereosinophilic syndrome with imatinib mesylate.

Patients with idiopathic hypereosinophilic syndrome (HES) show persistent hypereosinophilia of unknown etiology that is associated with end-organ damage. Different treatments, including the use of corticosteroids and cytotoxics, have been investigated for HES with modest success. We report a young patient with HES who developed stroke and remained refractory to conventional therapy. Therapy with imatinib mesylate, a selective tyrosine kinase inhibitor that is highly effective in treating patients with BCR-ABL-positive chronic myeloid leukemia, was tried with the patient. The result was impressive, with hematologic remission achieved rapidly. Our finding concurs with recent reports that imatinib mesylate may be a promising agent in the treatment of some cases of HES.