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Eosinophilia is a transient or sustained increase in the number of eosinophils in the tissues and/or blood with absolute blood eosinophil counts > 450 to 550 cells/µL.
Eosinophilia is caused due to allergies (asthma, atopic dermatitis, sinusitis), drugs (penicillins, ibuprofen, allopurinol, carbamazepine), parasites (ascariasis, cysticercosis, schistosomiasis) and infections (fungi, virus), autoimmune diseases (eosinophilic granulomatosis with polyangiitis, IBD), malignancy (lymphoma, lung cancer), immunodeficiency (Job syndrome, Wiskott-Aldrich syndrome), and idiopathic reasons (hypereosinophilic syndromes).
Disease course
Clinical manifestations of eosinophilia are heterogeneous that depend on the underlying cause and the affected organs (lungs, heart, skin, blood vessels, kidneys, brain, sinuses) that can range from being asymptomatic to showing symptoms of rash, pruritus, erythema, angioedema, urticaria, hives, fever, fatigue, malaise, tissue swelling, myalgias, weight gain, splenomegaly, Stevens-Johnson syndrome, toxic epidermal necrolysis, thrombosis, and progressive HF.
Prognosis and risk of recurrence
Eosinophilia is associated with all-cause mortality with odds ratio of 1.16 (95% CI 1.09-1.24, p < 0.0001) and 1.60 (95% CI 1.35-1.91, p < 0.0001) for mild and severe eosinophilia, respectively.


Key sources

The following summarized guidelines for the evaluation and management of eosinophilia are prepared by our editorial team based on guidelines from the British Society for Haematology (BSH 2017). ...
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Diagnostic investigations

Clinical history: as per BSH 2017 guidelines, evaluate for the underlying cause of eosinophilia and for possible eosinophil-associated end-organ damage.
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  • Blood tests

  • Evaluation for end-organ damage

  • Serum tryptase estimation

  • FISH

Diagnostic procedures

Bone marrow biopsy: as per BSH 2017 guidelines, perform a bone marrow aspirate and biopsy in patients without an identifiable cause for eosinophilia and with negative peripheral blood analysis for FIP1L1-PDGFRA by FISH or nested RT-PCR. Assess for an underlying lymphoma or of the lymphocytic variant of hypereosinophilic syndrome, including consideration of immunophenotyping of peripheral blood and bone marrow lymphocytes and analysis for T-cell receptor gene rearrangement.

Medical management

Patients with severe eosinophilia
As per BSH 2017 guidelines:
Initiate high-dose corticosteroids in patients requiring emergency treatment for severe or life-threatening eosinophilia.
Administer concomitant ivermectin in patients at risk for Strongyloides infection, to prevent potentially fatal hyperinfection.

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  • Patients with clonal eosinophilia

  • Patients with idiopathic hypereosinophilic syndrome

Surgical interventions

Hemopoietic stem cell transplantation: as per BSH 2017 guidelines, consider hemopoietic stem cell transplantation for patients with clonal eosinophilia with FGFR 1 rearrangement; patients with chronic eosinophilic leukemia, not otherwise specified; and patients hypereosinophilic syndromes patients refractory to or intolerant of both conventional TKI therapy and experimental medical therapy, where available, or who display progressive end-organ damage.