 The identification of the FIP1L1-PDGFRA fusion gene provides a molecular explanation for the pathogenesis of approximately half of the patients with the hypereosinophilic syndrome (HES).     ///    "All imatinib treated FIP1L1-PDGFRA positive CEL patients achieve hematological and cytogenetic remission, and the majority of patients also achieve a molecular remission with the fusion gene no longer detectable in blood, even by the most sensitive PCR techniques.. "    ///    "FIP1L1-PDGFRA positive CEL patients respond very well to imatinib therapy, some of which are remarkable responses with normalization of the blood counts within 2 weeks after start of the therapy. "    ///    "A diagnostic test to identify FIP1L1-PDGFRA positive HES cases (subsequently reclassified as chronic eosinophilic leukemia, CEL) is now available. "