PDGFRA and Chronic Eosinophilic Leukemia, Not Otherwise Specified: Interestingly, hFip1 also comprises the N-terminal part of a fusion protein with platelet-derived growth factor receptor alpha (PDGFRα), which causes 14–60% the incidents of hypereosinophilic syndrome/chronic eosinophilic leukemia (Cools et al., 2003; Gotlib and Cools, 2008; Li et al., 2012a).