TABLE 1.
Definition of Hypereosinophilia (HE) and of the Hypereosinophilic Syndrome (HES)
| Name/term | Abbreviation | Definition and criteria |
|---|---|---|
| Hypereosinophilia | HE | ≥1.5 eosinophils ×109/L peripheral blood on two examinations (interval ≥2 weeks). a |
| Tissue HE may or may not be detected. | ||
| Tissue hypereosinophilia | Tissue HE | One or more of the following applies: |
| a) the percentage of eosinophils in bone marrow section exceeds 20% of all nucleated cells, and/or | ||
| b) a pathologist is of the opinion that tissue infiltration by eosinophils is extensive and/or | ||
| c) marked deposition of eosinophil granule proteins is found (in the absence or presence of tissue infiltration by eosinophils) | ||
| Hypereosinophilic syndrome | HES | a) criteria for blood HE fulfilled and: |
| b) organ damage and/or dysfunction attributable to tissue HE b and: | ||
| c) exclusion of other disorders or condition as major reason for organ damage | ||
| Tissue‐restricted HES c (organ‐restricted HES) | a) tissue HE but criteria for blood HE not fulfilled and: | |
| b) organ damage and/or dysfunction attributable to tissue HE b and: | ||
| c) exclusion of other disorders or conditions as major reason for organ damage |
Abbreviations: eMBP1, eosinophil major basic protein 1; EPX, eosinophil peroxidase; HE, hypereosinophilia; HES, hypereosinophilic syndrome(s).
In patients with chronic myeloid leukemia (CML) or acute myeloid leukemia (AML), HE is defined by an absolute eosinophil count of ≥1.5 × 109/L peripheral blood and a relative eosinophil count of at least 10% (both for at least 2 weeks).
HE‐related organ damage (damage attributable to HE): organ dysfunction with marked tissue eosinophil infiltrates or/and extensive deposition of eosinophil‐derived proteins such as eMBP1 or EPX (in the presence or absence of marked tissue eosinophils) and typical clinical, histopathological and laboratory‐based signs of HE‐induced organ damage. When considering (establishing) the diagnosis HES is important to exclude all other etiologies as primary reason of organ damage.
When blood HE is not recorded in a patient with tissue HE and clear signs of HES, the (provisional) diagnosis of tissue‐restricted (organ‐restricted) HES can be established.