Page 90 - AIDSBK23C

Page 90

CYTOMEGALOVIRUS INFECTIONS

Cytomegalovirus (CMV) is a very frequent infection complicating AIDS. The
seroprevalence of CMV is very high in patients infected with HIV. Venereal transmission
appears to be the most common route of infection in adults, though CMV can also be spread
through genital secretions, oropharyngeal sections, urine, breast milk, and blood. Asymptomatic
persons who have primary infection or reactivation of latent infection can shed virus. Most
patients with AIDS who develop clinical signs and symptoms of CMV infection probably have
reactivation of previous infection rather than primary infection.[418]
CMV is the most widely distributed opportunistic agent seen with AIDS and, unlike
Pneumocystis jiroveci (carinii), which nearly always involves only the lung, CMV can and does
involve many organs. The most clinically significant sites of involvement are lung,
gastrointestinal tract, brain, and eye. In a large autopsy series, CMV occurred most frequently in
adrenal and respiratory tract, followed by the gastrointestinal tract, central nervous system, and
eye, infrequently in spleen and genitourinary tract, and rarely in lymph node, skin, liver, bone
marrow, or heart (Table 5).[418]
The diagnosis of CMV retinopathy, one of the most clinically debilitating complications
of CMV infection, is made on funduscopic examination because of the inability to obtain tissue
from this site. Many patients with CMV retinopathy develop partial or complete blindness.
Additional clinical manifestations of CMV infection can include altered mental status,
pneumonitis with non-productive cough, colitis or esophagitis with or without gastrointestinal
hemorrhage, adrenal insufficiency, hepatitis, or radiculitis.
Cytomegalovirus can be detected through culture of blood, fluids, or tissues containing
the virus, but culture methods are expensive and time consuming, and the presence of CMV does
not always correlate with infection causing disease. Serologic titers are not very useful to detect
CMV infection, since at least 30% of persons without immunosuppression also have antibodies
to CMV, and the seroprevalence is very high among immunosuppressed persons. Changing
titers of antibodies may aid in the detection of response to therapy in some patients with
CMV.[418]
Examination of tissue biopsies obtained from pulmonary or gastrointestinal endoscopy by
routine light microscopy is often the simplest means for the diagnosis of CMV, but sensitivity is
decreased by sampling error, for diagnostic inclusions can be widely scattered or infrequent.
Immunofluorescent antibody staining of tissues may aid diagnostic screening in some cases.
Techniques to detect cytomegaloviral DNA by in situ hybridization or polymerase chain reaction
are more sensitive than light microscopy. The presence of CMV in bronchoalveolar lavage or
sputum specimens does not necessarily indicate a clinically important infection. At autopsy,
diagnosis is most often made histologically by finding characteristic CMV inclusions in the
adrenal gland or lung (Table 5).[419]
Cytomegalovirus is a DNA virus of the herpesvirus group. It produces an enlargement of
the infected cell, and microscopically with hematoxylin-eosin staining, a large 5 to 15 micron
sized violaceous to dark red intranuclear inclusion surrounded by a thin clear halo can be seen.
The nucleus of the infected cell is usually eccentrically positioned. More than one inclusion
body may be present. Additionally, the cytoplasm of infected cells may contain coarse dark
basophilic bodies 2 to 3 microns in size representing replication of virions in the cytoplasm. The
cell border is not prominent. In tissue sections the cytomegalic cells are large and distinctive (30