Guideline 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). 1 2 2 2 3 Definition 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/uL. 2 Epidemiology 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). 2 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. 2 Prognosis and risk of recurrence https://web.pathway.md/diseases/reclOsdLQ2ZMQsbQt 1/3 6/29/23, 4:17 AM Eosinophilia Pathway 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. 3 Guidelines 1. Diagnostic investigations Clinical history: evaluate for the underlying cause of eosinophilia and for possible eosinophil- associated end-organ damage. B Blood tests: obtain a full blood count, peripheral blood smear, routine tests of renal and liver function, a bone profile, LDH, ESR and/or CRP, as well as a vitamin B12 assay in all patients. B Evaluation for end-organ damage: assess for end-organ damage using CXR and/or CT of the thorax, echocardiography, serum troponin T, and pulmonary function tests. B Serum tryptase estimation: obtain serum tryptase levels if the differential diagnosis includes chronic eosinophilic leukemia or systemic mastocytosis. B Fluorescence in situ hybridisation (FISH): investigate patients with an eosinophil count of at least 1.5 10 cells/L with no obvious cause for a possible hematological neoplasm associated with clonal eosinophilia, initially by peripheral blood analysis for FIP1L1-PDGFRA by FISH or nested RT-PCR. B 2. Diagnostic procedures Bone marrow biopsy: 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. B 3. Medical management Patients with severe eosinophilia: Initiate high-dose corticosteroids in patients requiring emergency treatment for severe or life- threatening eosinophilia. B Administer concomitant ivermectin in patients at risk for Strongyloides infection, to prevent potentially fatal hyperinfection. B Patients with clonal eosinophilia: administer low-dose imatinib to patients with clonal eosinophilia and FIP1L1-PDGFRA, including patients presenting with acute leukemia. B https://web.pathway.md/diseases/reclOsdLQ2ZMQsbQt 2/3 6/29/23, 4:17 AM Eosinophilia Pathway Patients with idiopathic hypereosinophilic syndrome: administer high-dose corticosteroids in patients with severe or life-threatening eosinophilia in the context of idiopathic hypereosinophilic syndrome. B 4. Surgical interventions Hemopoietic stem cell transplantation: 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. C Clinical findings Symptoms Past medical history Diarrhea Allergic reactions Itching Asthma Runny nose Atopy Cancer Integument exam Eosinophilic granulomatosis with polyangiitis Rash Medications Parasite infections Histological findings Hematological findings Charcot-leyden crystals blood eosinophils References 1. Butt NM, Lambert J, Ali S et al. Guideline for the investigation and management of eosinophilia. Br J Haematol. 2017 Feb;176 4 553 572. Open 2. Anna Kovalszki, Peter F. Weller. Eosinophilia. Prim Care. 2016 Dec; 43 4 607 617. Open 3. Christen Lykkegaard Andersen, Volkert Dirk Siersma, Hans Carl Hasselbalch et al. Eosinophilia in routine blood samples and the subsequent risk of hematological malignancies and death. Am J Hematol. 2013 Oct;88 10 843 7. Open https://web.pathway.md/diseases/reclOsdLQ2ZMQsbQt 3/3