Eosinophilic Disorders

The answer first

Eosinophilia — an absolute eosinophil count above 0.5 × 10⁹/L — is a common incidental finding that the physician must triage with discipline: confirm it is persistent, search for end-organ damage, classify the cause into secondary (reactive), primary (clonal), and idiopathic categories, and only then commit to disease-specific therapy. ^{[1] [3]} The answer-first move in any long case is to decide whether the eosinophilia is harmless and explainable (atopy, drug, resolved parasitic infection), dangerous and organ-threatening (hypereosinophilic syndrome with cardiac, neurological, or thromboembolic involvement; eosinophilic granulomatosis with polyangiitis; eosinophilic myocarditis), or clonal and treatable with a targeted agent (FIP1L1-PDGFRA–positive disease responding to imatinib). ^{[1] [7] [8]}

For the FRACP candidate the eosinophilic long case rewards a one-sentence synthesis ("a 42-year-old man with adult-onset asthma, peripheral eosinophilia of 2.4 × 10⁹/L, mononeuritis multiplex and a positive MPO-ANCA"), a problem list ordered by threat to life (cardiac, neurological, thromboembolic), and a plan that integrates classification workup, induction therapy, primary prophylaxis against cardiac thrombus, and a named subspecialty pathway. ^{[1] [4]}

References12ShowHide

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2. [2]Klion AD Approach to the patient with suspected hypereosinophilic syndrome Hematology Am Soc Hematol Educ Program, 2022.PMID 36485140
3. [3]Taurisano G, Ruffi MC, Canalis S, et al. Hypereosinophilia: clinical and therapeutic approach in 2025 Curr Opin Allergy Clin Immunol, 2025.PMID 40396537
4. [4]Wechsler ME, Akuthota P, Jayne D, et al. Mepolizumab or Placebo for Eosinophilic Granulomatosis with Polyangiitis N Engl J Med, 2017.PMID 28514601
5. [5]Chung SA, Langford CA, Maz M, et al. 2021 American College of Rheumatology/Vasculitis Foundation Guideline for the Management of Antineutrophil Cytoplasmic Antibody-Associated Vasculitis Arthritis Rheumatol, 2021.PMID 34235894
6. [6]Brambatti M, Matassini MV, Adler ED, et al. Eosinophilic Myocarditis: Characteristics, Treatment, and Outcomes J Am Coll Cardiol, 2017.PMID 29096807
7. [7]Robyn J Imatinib-responsive hypereosinophilic syndrome Leuk Res, 2006.PMID 16530830
8. [8]Tennenbaum J, Groh M, Venditti L, et al. FIP1L1-PDGFRA-Associated Hypereosinophilic Syndrome as a Treatable Cause of Watershed Infarction Stroke, 2021.PMID 34304603
9. [9]Kuang FL, Legrand F, Makiya M, et al. Benralizumab for PDGFRA-Negative Hypereosinophilic Syndrome N Engl J Med, 2019.PMID 30943337
10. [10]Dellon ES, Rothenberg ME, Collins MH, et al. Dupilumab in Adults and Adolescents with Eosinophilic Esophagitis N Engl J Med, 2022.PMID 36546624
11. [11]Hama N, Abe R, Gibson A, et al. Drug-Induced Hypersensitivity Syndrome (DIHS)/Drug Reaction With Eosinophilia and Systemic Symptoms (DRESS): Clinical Features and Pathogenesis J Allergy Clin Immunol Pract, 2022.PMID 35176506
12. [12]Czeresnia JM, Weiss LM Strongyloides stercoralis Lung, 2022.PMID 35396957