[Interferon-alpha therapy in the myeloproliferative variants of hypereosinophilic syndrome].

Two cases of hypereosinophilic syndrome (HES) that seemed to be myeloproliferative disorders were treated with interferon-alpha (IFN-alpha). Case 1 was a 45-year-old man with HES who was unresponsive to prednisolone. Because Flaum's hematologic grading score was 8 points, he was diagnosed as a myeloproliferative variant of HES. Although his condition was well controlled by hydroxyurea (HU), cardio-pulmonary insufficiency with refractory eosinophilia developed after 4 years. Instead of HU, IFN-alpha dramatically decreased eosinophil counts, and the clinical situation has stabilized since. Case 2 was a 30-year-old man with HES whose grading score was 9 points. IFN-alpha therapy was started when an accelerated phase of neutrophil dominant with chromosomal abnormality (8 trisomy) occurred. However, he died because of no response to IFN-alpha and other chemotherapy. In both cases, studies of eosinophil colony formation revealed no excess of eosinophil colony-stimulating factor from their lymphocytes. Flaum's hematologic grading score was useful for the diagnosis of myeloproliferative variants of HES. IFN-alpha successfully induced hematologic remission in one case, and this therapy may be beneficial for these patients as a first line agent.