PDGFRB and Increased total eosinophil count: After ruling out the hypothesis of non−hematologic origin, testing for gene rearrangements associated with clonal eosinophilia, such as BCR::ABL1, PDGFRA, PDGFRB, FGFR1, PCM1::JAK2, and JAK2::V617F, did not yield any definitive clues.