Effective therapy for a severe case of the idiopathic hypereosinophilic syndrome

An 8-year-old boy with idiopathic hypereosinophilic syndrome (HES) is reported. He has been maintained in prolonged hematologic remission with vincristine and mercaptopurine despite an initial eosinophil count of 186 X 10(9)/L and a poor response to prednisone and hydroxyurea. Success with this combination of chemotherapeutic agents has not previously been reported in the management of HES. Progressive endomyocardial fibrosis required cardiac surgery 11 months after diagnosis. The management of this disorder is discussed with a review of the published literature.