The hypereosinophilic syndrome: dramatic response to therapeutic intervention.

The Hypereosinophilic Syndrome (HES) is a disease of unknown etiology and pathogenesis characterized by blood and bone marrow eosinophilia associated with infiltration of eosinophils into tissues and multi-system organ dysfunction. Patients with HES historically have very significant morbidity and a high mortality of 77% at 3 years. This study is a prospective (9 years) and retrospective (24 years) analysis of the therapy and prognosis of 26 patients with HES. Five patients (19%) showed no evidence of progressive organ system dysfunction and were given no therapy; all have done well. Sixteen patients with progressive organ dysfunction were treated with corticosteroids; 6 of the 16 (38%) had a good response and required no further therapy. Six of 8 patients who were corticosteroid unresponsive and had serious prognostic signs had excellent responses to hydroxyurea therapy, while 2 patients showed partial responses. Employing the above regimen, we have demonstrated that our 26 patients (including 12 with poor prognostic indicators) have a marked increase in survival (3 year mortality 4%) when compared with the historical control.