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DEFINITION

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  • Infectious mononucleosis is defined as any blood lymphocytosis induced in response to an infectious agent.

  • Usually greater than 50% of the circulating white cells are lymphocytes, more than 10% of which have the morphology of reactive lymphocytes (Figure 52–1).

  • Table 52–1 lists the etiologic agents that produce mononucleosis.

  • Pharyngeal form:

    — A sore throat is preceded by 1 to 2 weeks of lethargy.

    — Epstein-Barr virus (EBV) generally is the cause.

  • Glandular form without pharyngitis:

    — Lymph node enlargement occurs.

    — The usual cause is agents other than EBV (eg, Toxoplasma gondii).

  • Typhoidal form:

    — Lethargy with fever or diarrhea without pharyngitis, usually as a consequence of cytomegalovirus (CMV), is characteristic.

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FIGURE 52–1

AD. Blood films from patients with Epstein-Barr virus–induced mononucleosis. These reactive lymphocytes exhibit the characteristic changes seen in patients with infectious mononucleosis: large lymphocytes with abundant cytoplasm. The cytoplasmic margin often spreads around (is indented by) neighboring red cells and the margin may take on a densely basophilic coloration. This type of reactive T lymphocyte may be seen a variety of diseases and is not specific changes but are characteristic. (Reproduced with permission from Lichtman’s Atlas of Hematology, www.accessmedicine.com.)

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Table Graphic Jump Location
TABLE 52–1ETIOLOGIC AGENTS ASSOCIATED WITH MONONUCLEOSIS SYNDROME
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ETIOLOGY AND PATHOGENESIS

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  • The caused is two members of the herpes virus family: EBV or CMV.

  • After the early phase of fever, which lasts for 3 to 7 days, laboratory abnormalities include a blood lymphocyte proportion greater than 50%, often with greater than 10% reactive lymphocytes.

  • Table 52–2 lists other complications of EBV and CMV mononucleosis.

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TABLE 52–2COMPLICATIONS IN PATIENTS WITH EBV OR CMV MONONUCLEOSIS
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FEATURES OF MONONUCLEOSIS CAUSED BY EACH ETIOLOGIC AGENT

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  • Table 52–3 list the signs and symptoms associated with EBV and CMV mononucleosis.

  • Target cell for EBV mononucleosis is the B lymphocyte.

  • Target cell for CMV mononucleosis is the macrophage.

  • The “mononucleosis” for both is ...

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