Hypereosinophilic Syndrome

Abstract
In some patients with idiopathic hypereosinophilic syndrome, Cools et al. (March 27 issue)1 detected a FIP1L1-PDGFRA fusion gene that was associated with a dramatic response to imatinib mesylate. Along with the recent description of the “lymphocytic variant” of the hypereosinophilic syndrome,2 their observation will provide clinicians with cornerstones for tailoring the management of this heterogeneous disease according to the underlying pathogenic mechanisms.