Evaluation includes assessment for reactive causes of eosinophilia (vasculitis such as eosinophilic granulomatosis and polyangiitis or Churg-Strauss, parasitic infection, autoimmune disease, immunoglobulinG4-related disease, medications and other causes), genetic lesions characteristic of clonal myeloid disorders (platelet-derived growth factor receptor-α, platelet-derived growth factor receptor-β and fibroblast growth factor receptor 1) and flow cytometry and molecular studies for the aberrant T cells characteristic of lymphocyte-variant HES .
Chronic eosinophilic leukemia not otherwise specified should be distinguished from both PDGFR-rearranged or FGFR1-rearranged neoplasms and hypereosinophilic syndrome.
HES and CEL-NOC are considered distinct from molecularly defined eosinophilic disorders, such as those associated with activating mutations of PDGFR (PDGFRA and PDGFRB) and fibroblast growth factor receptor-1.
Our aims were: a) to use interphase-fluorescent in situ hybridization (FISH) to detect the cryptic 4q12 deletion; b) to compare the clinico-hematologic features of 4q-/CEL with other HES; c) to investigate whether PDGFRB, FGFR1, ABL1, and ETV6-activated tyrosine kinases are rearranged in CEL/HES.
Interestingly, imatinib mesylate treatment, at a higher dose level (400 mg/day), might induce either partial or short-lived complete remissions in HES that is not associated with the aforementioned PDGFR mutations.