Eosinophilia D72.1

Eosinophilia is defined as an elevated eosinophil concentration in the peripheral blood.

• Eosinophil counts of > 500/μl correspond to a weak eosinophilia.
• Eosinophil counts of 1500/μl correspond to moderate eosinophilia
• Eosinophil counts of > 5000/μl correspond to severe eosinophilia.

The causes are heterogeneous and require differentiation between a:

• primary eosinophilia due to a haematological neoplasm, e.g. eosinophil leukaemia (CEL)
• a secondary eosinophilia
• a reactive eosinophilia, e.g. caused by parasitic infestation or allergic reactions
• an ideopathic eosinophilia(hypereosinophilia syndrome - HES).

In the case of eosinophil leukemia (chronic eosinophil leukemia- CEL-NOS), the persistent eosinophilia is due to clonal proliferation of an eosinophil precursor.

Within the WHO major category, CEL-NOS is classified in the myeloproliferative neoplasia (MPN) group and can be diagnosed by an eosinophil concentration > 1500/μl, evidence of clonal cytogenetic or molecular genetic markers, and exclusion of the following criteria:

• Absence of a Philadelphia chromosome or a PDGFRA, PDGFRB, FGFR1, or JAK2 rearrangement.
• Exclusion of other acute or chronic myeloproliferative and/or myelodysplastic neoplasms.
• ≥ 20% blasts in peripheral blood or bone marrow.

S.a. Eosinophilia and skin lesions

1. Wozel G (2007) Eosinophilia dermatoses. Dermatologist 58: 347-360