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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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