Using of low-dose imatinib mesylate (100?mg/day) a hematological and molecular remission in all patients displaying the FIP1L1-PDGFRA fusion gene was observed.     ///    FIP1L1-PDGFRA fusion is a clonal marker for the diagnosis and treatment of HES.     ///    "Patients with FIP1L1-PDGFRA fusion presented with more bone marrow eosinophils and peripheral blood eosinophilia as well as anemia, leukocytosis and thrombocytopenia. "    ///    FIP1L1-PDGFRA fusion was found in eight patients. 