In clonal eosinophilia, although corticosteroids generally do not normalize absolute eosinophil counts, they may reduce eosinophil activation and lower their cytotoxic potential pending a precise molecular diagnosis and onset of a specific treatment (as detailed in “Management of FIP1L1::PDGFRA–positive chronic eosinophilic leukemia” and “Management of non-F/P-associated clonal HES” Sections). The gene discussed is PDGFRA; the disease is Chronic Eosinophilic Leukemia, Not Otherwise Specified.