Page 309 - Review of Medical Microbiology and Immunology ( PDFDrive )

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PART IV Clinical Virology
298

mebooksfree.com mebooksfree.com mebooksfree.com FIGURE 37–9 Atypical lymphocytes in infectious mononucle- mebooksfree.com
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osis—note two atypical lymphocytes, each with an enlarged nucleus
and abundant cytoplasm on the left side. The lymphocyte on the
FIGURE 37–8
Hairy leukoplakia—note whitish plaques on lat-
eral aspect of tongue caused by Epstein–Barr virus. (Reproduced with
Braunwald E, Kasper DL et al, eds. Harrison’s Principles of Internal Medicine. 17th ed.
permission from Wolff K, Johnson R. Fitzpatrick’s Color Atlas & Synopsis of Clinical Der-
New York: McGraw-Hill, 2008. Copyright © 2008 by The McGraw-Hill Companies, Inc.)
matology. 6th ed. New York: McGraw-Hill, 2009. Copyright © 2009 by The McGraw- right side appears normal. (Reproduced with permission from Fauci AS,
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Hill Companies, Inc.)
immunosuppression required to prevent rejection of the
lymphocytes, it is a technically difficult procedure and is
graft. The lymphoma will regress if the degree of immuno-
suppression is reduced.
lymphocytes; its presence is detected by fluorescent anti-
body staining of the nuclear antigen.
Laboratory Diagnosis
Treatment
The diagnosis of infectious mononucleosis in the clinical
laboratory is based primarily on two approaches:
No antiviral therapy is necessary for uncomplicated infec-
(1) In the hematologic approach, absolute lymphocyto-
EBV, but administration of high doses may be useful in
sis occurs, and as many as 30% abnormal lymphocytes are
life-threatening EBV infections.
seen on a smear. These atypical lymphs are enlarged, have tious mononucleosis. Acyclovir has little activity against
an expanded nucleus, and an abundant, often vacuolated
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Prevention
cytoplasm (Figure 37–9). They are cytotoxic T cells that are
reacting against the EBV-infected B cells.
There is no EBV vaccine.
(2) In the immunologic approach, there are two types
of serologic tests: (a) The heterophil antibody test is use-
ful for the early diagnosis of infectious mononucleosis
EBV infection is associated with cancers of lymphoid
because it is usually positive by week 2 of illness. However,
origin: Burkitt’s lymphoma in African children, other
because the antibody titer declines after recovery, it is not
B-cell lymphomas, nasopharyngeal carcinoma in the
useful for detection of prior infection. The Monospot test
Chinese population, and thymic carcinoma in the United
is often used to detect the heterophil antibody; it is more
States. The initial evidence of an association of EBV
sensitive, more specific, and less expensive than the tube
agglutination test. (b) The EBV-specific antibody tests are
EBV by the lymphoma cells in culture. In fact, this was
used primarily in diagnostically difficult cases. The IgM
how EBV was discovered by Epstein and Barr in 1964.
VCA antibody response can be used to detect early illness; infection with Burkitt’s lymphoma was the production of
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Additional evidence includes the finding of EBV DNA
the IgG VCA antibody response can be used to detect prior
and EBNA in the cells of nasopharyngeal and thymic
infection. In certain instances, antibodies to EA and EBNA
carcinomas. EBV can induce malignant transformation
can be useful diagnostically.
Although EBV can be isolated from clinical samples
In Burkitt’s lymphoma, oncogenesis is a function of the
such as saliva by morphologic transformation of cord blood
translocation of the c-myc oncogene to a site adjacent to
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