| The following terms are currently used in medical literature to qualify different patient subsets among those fulfilling the diagnostic criteria of HES:
FIP1L1-PDGFRA(F/P)-associated HES, or F/P+ HES, for patients with clonal hypereosinophilia due to a sporadic hematopoiëtic stem cell chromosomal rearrangement resulting in fusion of two genes (FIP1L1 and PDGFRA) on 4q12; these patients are more appropriately classified as F/P+ chronic eosinophilic leukemia.
Chronic eosinophilic leukemia (CEL), for patients in whom clonality of eosinophils has been demonstrated (including those with the FIP1L1-PDGFRA fusion), or who present increased blasts; occasional reports indicate that some patients with CEL progress towards acute myeloid or eosinophilic leukemia.
Lymphocytic-HES (L-HES), for patients with chronic reactive (polyclonal) hypereosinophilia secondary to IL-5 over-production by T cells.
Myeloproliferative-HES (M-HES) may be used for patients with an array of clinical and biological features suggesting the possible existence of an underlying myeloproliferative disorder associated with hypereosinophilia, although underlying molecular defects are not detected (including increased serum vitamin B12, hepato- and/or splenomegaly, anemia and/or thrombocytopenia, circulating myeloid precursors, dysplastic eosinophils, bone marrow hypercellularity with left shift in maturation, myelofibrosis, increased serum tryptase, and response to imatinib); this term is occasionally extended more largely to include patients with known molecular defects (e.g.