Primary Hypereosinophilic Syndromes (HES) - Diagnosis ...

Primary Hypereosinophilic Syndromes (HES) - Diagnosis and Management

Myelodysplastic HES: acute/chronic eosinophilic leukemia, PDGFRA-associated MPN → clonal expansion of Eos; 80% pts have FIP1L1-PDGFRA fusion gene; remainder have PDGFRA, FGFR1, JAK2 rearrangements

 • Dx: anemia, thrombocytopenia,  tryptase,  B12, special slide (dysplastic eosinophils), flow cytometry (PDGFRA, BCRABL1, JAK2, FGFR1, KIT), BM Bx (fibrosis, hypercellularity)

 • Tx: if PDGDR+, imatinib; if JAK2+, JAK2 inhibitor; if FGFR1+, chemo; 2nd line or no rearrangment: hydroxyurea, IFN-α, other TKI/empiric imatinib

Lymphocytic HES: clonal lymphocyte expansion → ↑ cytokines that stimulate eosinophil differentiation. Often present w/ skin/soft tissue manifestations. Up to 25% risk of progression to lymphoma.

 • Dx: flow cytometry for CD3, CD4

 • Tx: steroids; 2nd line: IFN-α, hydroxyurea, mepolizumab (anti-IL-5), alemtuzumab

Idiopathic HES: eosinophilia without identified cause and evidence of end-organ damage → consider ANCA-neg EGPA (50% cases)

 • Tx: steroids; 2nd line: hydroxyurea, IFN-α, imatinib, mepolizumab, alemtuzumab

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