The efficacy of imatinib mesylate in patients with FIP1L1-PDGFR -positive hypereosinophilic syndrome. Results of a multicenter prospective study

All patients meeting the criteria for idiopathic or primary HES should be screened for the FIP1L1-PDGFRalpha rearrangement. For all patients with this rearrangement, chronic imatinib treatment at doses as low as 100 mg daily ensures complete and durable responses.