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Chapter 32: Eosinophils and Related Disorders

EOSINOPHIL PRODUCTION AND COUNTS

  • Eosinophils differentiate from the hematopoietic stem cell in the marrow, migrate into the blood, and circulate with a half-life of 18 hours before entering tissues. Eosinophils are primarily tissue dwelling, with 300 cells in the tissues for every blood eosinophil.

  • The normal blood absolute eosinophil count in adults is less than 0.4 × 109 cells/L; it is higher in neonates.

  • The normal adult marrow contains approximately 3% eosinophils.

DEGREE AND CAUSES OF EOSINOPHILIA

  • The degree of eosinophilia is described as:

    — Mild (< 1.0 × 109 eosinophils/L)

    — Moderate (1.0 to 5.0 × 109 eosinophils/L)

    — Marked (> 5.0 × 109 eosinophils/L)

  • The most common causes of eosinophilia include:

    — Throughout the world: infections with helminthic parasites

    — In industrialized countries: asthma and other allergic disorders (drug allergy, allergic rhinitis, atopic dermatitis)

    — Allergic diseases: generally only mild eosinophilia

    — Major causes: listed in Table 32–1

TABLE 32–1CAUSES OF EOSINOPHILIA
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TABLE 32–1 CAUSES OF EOSINOPHILIA
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Disease Frequency Usual Degree of Eosinophilia Comment
Infections
Parasitic Common worldwide Moderate to high  
Bacterial Rare   Usually cause eosinopenia, although serum ECP levels may be raised, suggesting eosinophil involvement in tissue.
Mycobacterial Rare   More often secondary to drug therapy.
Invasive fungal Unusual   Apart from allergic reactions, which are common, and coccidioidomycosis, in which as many as 88% of patients have an eosinophilia.
Rickettsial infections Rare    
Fungi Rare   Cryptococcus reported as causing CSF eosinophilia.
Viral infections Rare   There are occasional case reports of an eosinophilia in a variety of viral infections, including herpes and HIV infection.
Allergic diseases
Allergic rhinitis Common worldwide Mild  
Atopic dermatitis Common especially children Mild to moderate  
Urticaria/angioedema Common Variable Eosinophilia seen in skin even with normal blood count.
Fungal allergy Common Mild to high Immunoglobulin (Ig) E sensitization to thermotolerant colonizing yeast (eg, Candida albicans) and molds (eg, Aspergillus fumigatus) is a common cause of an eosinophilia.
Asthma Common Mild Syndrome of intrinsic asthma, nasal polyps, and aspirin intolerance are associated with higher-than-usual eosinophil counts.
Drug reactions
Many drugs Uncommon Mild to high Antibiotics, NSAIDs, and antipsychotics are the most common groups; count usually returns to normal on stopping drug.
Neoplasms
Acute eosinophilic leukemia Rare High  
Acute myelogenous leukemia with marrow eosinophilia Uncommon Mild to high in marrow only Often associated with chromosome 16 abnormalities.
Chronic eosinophilic leukemia Rare High See text on HES.
Chronic myelogenous leukemia Uncommon Moderate to high Raised eosinophil counts can be seen uncommonly in chronic myelogenous leukemia.
Lymphomas Uncommon Moderate Often intense tissue eosinophilia with moderately elevated blood eosinophil count; Hodgkin lymphoma most common type. T-cell lymphomas elaborating IL-5 or other eosinopoietic cytokines.
Langerhans cell histiocytosis Uncommon Mild Intense tissue eosinophilia in granulomata but blood eosinophilia unusual.
Solid tumors Uncommon Mild to high Many different tumors reported.

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