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Chapter 34: Eosinophils and Their Diseases

EOSINOPHIL COUNTS

  • The normal absolute eosinophil count in adults is less than 0.5 × 109 cells/L.

  • The eosinophil count is higher in neonates.

  • Eosinophils are primarily tissue dwelling, with 300 cells in the tissues for every blood eosinophil.

CAUSES OF EOSINOPHILIA

  • The degree of eosinophilia is described as:

    — Mild (0.5 to 1.5 × 109 eosinophils/L).

    — Moderate (1.5 to 5.0 × 109 eosinophils/L).

    — Marked (>5.0 × 109 eosinophils/L).

  • The most common causes of eosinophilia include:

    — Worldwide: infections with helminthic parasites.

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

    — Allergic diseases generally result in only mild eosinophilia.

    — The major causes of eosinophilia are listed in Table 34–1.

TABLE 34–1CAUSES OF AN EOSINOPHILIA
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TABLE 34–1 CAUSES OF AN EOSINOPHILIA
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 Rare 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
Urticaria/angioedema Common Variable Eosinophilia seen in skin even with normal blood count.
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.
Musculoskeletal disorders
Rheumatoid arthritis Uncommon Mild to high Occasional case reports. More usually secondary to therapy.
Eosinophilic fasciitis Rare High
Gastrointestinal disorders
Eosinophilic gastroenteritis Rare Mild to moderate As with many GI diseases there is often a marked tissue eosinophilia with only a mild or no blood eosinophilia.
Eosinophilic esophagitis Increasingly recognized Mild Marked tissue eosinophilia with mild blood eosinophilia.
Celiac disease Uncommon None Tissue eosinophilia.
Inflammatory bowel disease Eosinophils seen in ...

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