A subset of HES patients presents an interstitial deletion in chromosome 4q12, which leads to the expression of an imatinib-responsive fusion gene, FIP1L1-PDGFRA.     ///    "We treated seven CEL and HES patients, six of which expressed FIP1L1-PDGFRA, with imatinib using initial daily doses ranging from 100 to 400 mg. "    ///    "All imatinib-treated patients achieved a complete haematological remission (CHR), and five of the six patients with FIP1L1-PDGFRA expression exhibited molecular remission. "