Eosinophilia



Eosinophilia


Carla S. Wilson, MD, PhD





Key Facts


Terminology



  • Absolute eosinophil count > 0.5 × 109/L, independent of age


Etiology/Pathogenesis



  • Reactive eosinophilia is usually caused by eosinopoietic cytokines, primarily IL-5 and GM-CSF


  • In industrialized countries allergens are most common cause of eosinophilia


  • In hospitalized patients medications are most common cause


  • In nonindustrialized countries parasites are most common cause


  • Activated eosinophils release proinflammatory mediators that cause tissue damage


  • Intravascular degranulation of eosinophils causes



    • Generalized endothelial damage


    • Endomyocardial fibrosis


    • Marked propensity for thrombus formation


Clinical Issues



  • Initial evaluation requires detailed history, physical examination, complete blood count, and blood film evaluation


Microscopic Pathology



  • Eosinophil atypia may be seen in both reactive and neoplastic disorders


  • Bone marrow is often normocellular unless associated with an autoimmune or neoplastic disorder


Top Differential Diagnoses



  • Idiopathic hypereosinophilic syndrome (HES)



    • Eosinophil count > 1.5 × 109/L for > 6 months


    • No tissue damage






Mature eosinophils are 10-15 um in size. The cytoplasmic, orange-red, refractile granules most easily distinguish the eosinophil in this image from the monocyte and neutrophil.






Approximately 80% of circulating eosinophils typically have 2 equally sized nuclear lobes, as illustrated in this peripheral blood smear with increased eosinophils.


TERMINOLOGY


Synonyms



  • Increased eosinophils


  • Reactive eosinophilia


  • Secondary eosinophilia


  • Eosinophilic hyperplasia


  • Absolute eosinophilia


Definitions



  • Absolute eosinophil count > 0.5 × 109/L, independent of age


  • Arbitrary ranges include



    • Mild (0.6-1.5 × 109/L)


    • Moderate (1.6-5.0 × 109/L)


    • Severe (> 5 × 109/L)


ETIOLOGY/PATHOGENESIS


Environmental Exposure



  • Allergies



    • Asthma


    • Hayfever


    • Allergic rhinitis


    • Sinusitis


  • Drug hypersensitivity



    • Numerous drugs


    • Recombinant cytokine therapy


Infectious Agents



  • Parasites: Helminths



    • Ascariasis


    • Hookworm


    • Filariasis


    • Schistosomiasis


    • Trichinosis


    • Strongyloidiasis


    • Cysticercosis


    • Echinococcosis


    • Paragonimiasis


    • Toxocariasis


    • Visceral larva migrans


  • Fungal



    • Cryptococcosis


    • Aspergillosis


    • Coccidioidomycosis


    • Histoplasmosis


    • Blastomycosis


  • Protozoal



    • Isospora belli


    • Dientamoeba fragilis


  • Bacterial


  • Viral



    • Human T-cell lymphotrophic virus


    • West Nile virus


Underlying Illness



  • Pulmonary disorders



    • Loeffler syndrome


    • Hypersensitivity pneumonitis


    • Bronchiectasis


    • Pneumonia


    • Churg-Strauss syndrome


  • Skin lesions



    • Atopic dermatitis


    • Urticaria


    • Pemphigus


    • Bullous pemphigoid


    • Angiolymphoid hyperplasia


    • Wells syndrome


    • Eosinophilic panniculitis


  • Gastrointestinal disease



    • Celiac disease


    • Inflammatory bowel disease


    • Eosinophilic gastroenteritis


    • Chronic pancreatitis


Immunologic Disorders



  • Polyarteritis nodosa



  • Kimura disease


  • Churg-Strauss syndrome


  • Sarcoidosis


  • Fasciitis


  • Collagen vascular diseases



    • Scleroderma


    • Systemic lupus erythematosus


  • Severe combined immunodeficiency


  • Allergic angitis


Neoplastic Processes; Eosinophils Nonneoplastic



  • Classical Hodgkin lymphoma


  • T-cell lymphoproliferative disorders


  • B-lymphoblastic leukemia with t(5;14)(q31;q32) IL3-IGH@


  • Langerhans cell histiocytosis


  • Myelodysplastic syndromes


  • Aberrant T-cell population (T cells may or may not be clonal)


  • Natural killer (NK) cell neoplasms


  • Carcinoma (paraneoplastic syndrome associated)


Pathogenesis



  • Cytokine-producing constituents in secondary (reactive) eosinophilia



    • Activated T-cells (Th2)


    • Mast cells


    • Stromal cells


    • Various neoplastic cells (e.g., lymphoma cells)


  • Cytokines that stimulate eosinophil production in bone marrow



    • IL-5


    • IL-3


    • IL-2


    • GM-CSF


  • Sustained cytokine production linked to chronic eosinophilia



    • Constitutive IL-3 activation in B-lymphoblastic leukemia with t(5; 14) IL3-IGH@


  • Eosinophil maturation takes approximately 5 days


  • Eosinophils circulate 18-24 hours before migrating into tissues


  • Chemotactic factors recruit eosinophils from blood into tissue



    • Eotaxin


    • IL-5


  • Majority of eosinophils are in tissues


  • Activated eosinophils release proinflammatory mediators that cause tissue damage


  • Intravascular degranulation of eosinophils causes



    • Generalized endothelial damage


    • Endomyocardial fibrosis


    • Marked propensity for thrombus formation


  • In industrialized countries allergens are most common cause


  • In hospitalized patients medications are most common cause


  • In nonindustrialized countries parasites most common cause

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Jun 13, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Eosinophilia

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