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DEFINITION

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

  • Usually greater than 50 percent of the circulating white cells are lymphocytes, more than 10 percent of which have the morphology of reactive lymphocytes (see Fig. 53–1).

  • Table 53–1 lists the etiologic agents that produce mononucleosis.

  • Pharyngeal form:

    — Sore throat preceded by 1 to 2 weeks of lethargy.

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

  • Glandular form without pharyngitis:

    — Lymph node enlargement.

    — Usually caused by agents other than EBV, e.g., Toxoplasma gondii.

  • Typhoidal form:

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

FIGURE 53–1

AD. Blood films from patients with EBV-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.)

(Source: Williams Hematology, 8th ed, Chap. 84, Fig. 84–1, p. 1202.)

TABLE 53–1ETIOLOGIC AGENTS ASSOCIATED WITH MONONUCLEOSIS SYNDROME

ETIOLOGY AND PATHOGENESIS

  • Caused by 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 percent, often with greater than 10 percent reactive lymphocytes.

  • Table 53–2 lists other complications of EBV and CMV mononucleosis.

TABLE 53–2COMPLICATIONS IN PATIENTS WITH EBV OR CMV MONONUCLEOSIS

FEATURES OF MONONUCLEOSIS CAUSED BY EACH ETIOLOGIC AGENT

  • Table 53–3 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 ...

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