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U N I T 4
Infection and Immunity
HIV infection.
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Aphthous ulcers presumed secondary
to HIV are also common. Persons experiencing these
infections usually complain of painful swallowing or
retrosternal pain. Endoscopy or barium esophagogra-
phy is required for definitive diagnosis.
Diarrhea or gastroenteritis is a common complaint
in persons with HIV infection. Although diarrhea is
often a side effect of medications used to treat HIV,
it should be evaluated for the same common causes
as in the general population. The most common pro-
tozoal opportunistic infection that causes diarrhea is
Cryptosporidium parvum.
Clinical features of cryp-
tosporidiosis can range from mild diarrhea to severe,
watery diarrhea with a loss of up to several liters of
water per day, as well as malabsorption, electrolyte
disturbances, dehydration, and weight loss. Other
organisms that cause gastroenteritis and diarrhea are
Salmonella,
CMV,
Clostridium difficile, Escherichia
coli, Shigella, Giardia,
and microsporidia.
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These
organisms are identified by examination of stool cul-
tures or endoscopy.
Nervous SystemManifestations.
Human immunode-
ficiency virus infection, particularly in the late stages of
severe immunocompromise, leaves the nervous system
vulnerable to an array of neurologic disorders, including
neurocognitive disorders, toxoplasmosis, and progres-
sive multifocal leukoencephalopathy.
HIV-associated neurocognitive disorders (HANDs)
is a syndrome of cognitive impairment with motor dys-
function or behavioral/psychosocial symptoms associ-
ated with HIV infection itself.
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In 2007, the National
Institute of Mental Health and National Institute of
Neurologic Diseases and Stroke developed a new clas-
sification with standardized diagnostic criteria for
HANDs. The three conditions comprising HANDs
are HIV-associated asymptomatic neurocognitive
impairment, HIV-associated mild neurocognitive dis-
order, and HIV-associated dementia, formerly known
as
AIDS dementia complex
.
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The clinical features
of HIV-associated dementia, which is usually a late
complication of HIV infection, include impairment of
attention and concentration, slowing of mental and
motor speed and agility, and apathetic behavior. There
is no specific treatment for HAND, but HAART com-
prised of medications which penetrate the blood-brain
barrier is considered the best therapeutic option at this
time.
Toxoplasmosis
is a common opportunistic infection
in persons with AIDS. The organism responsible,
T.
gondii,
is a parasite that most often affects the CNS.
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Toxoplasmosis usually is a reactivation of a latent
T. gondii
infection that has been dormant in the CNS. The
typical presentation includes fever, headaches, and neu-
rologic dysfunction, including confusion and lethargy,
visual disturbances, and seizures. Computed tomogra-
phy scans or, preferably, magnetic resonance imaging
(MRI) should be performed immediately to detect the
presence of neurologic lesions. Prophylactic treatment
with trimethoprim-sulfamethoxazole or an alternative
agent, which is also used for prevention of
P. jiroveci
pneumonia, is effective against
T. gondii
.
Progressive multifocal leukoencephalopathy
(PML) is
a demyelinating disease of the white matter of the brain
caused by the JC virus, a DNA papovavirus that attacks
the oligodendrocytes.
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PML advances slowly, and is
characterized by progressive limb weakness, sensory loss,
difficulty controlling the digits, visual disturbances, subtle
alterations in mental status, hemiparesis, ataxia, diplopia,
and seizures.
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The mortality rate is high, and the average
survival time is 2 to 4 months after diagnosis. Diagnosis
is suspected based on clinical findings and an MRI, and
confirmed by the presence of the JC virus in the cere-
brospinal fluid.
66
There is no proven cure for PML, but
improvement can occur after starting effective HAART.
Malignancies
Persons with AIDS have a high incidence of certainmalig-
nancies, especially Kaposi sarcoma (KS), non-Hodgkin
lymphoma, and noninvasive cervical carcinoma. The
increased incidence of malignancies probably is a func-
tion of impaired cell-mediated immunity. As persons
with HIV infection are living longer, there has been
increasing incidence of age- and gender-specific malig-
nancies.
67
Non–AIDS-defining malignancies account
for more morbidity and mortality than AIDS-defining
malignancies in the HAART era.
Kaposi sarcoma
is a malignancy of the endothelial
cells that line small blood vessels.
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An opportunis-
tic cancer, KS occurs in immunosuppressed persons
(e.g., transplant recipients or persons with AIDS).
Kaposi sarcoma was one of the first and most com-
mon opportunistic cancers associated with AIDS.
Since the introduction of HAART, the incidence of
KS has decreased dramatically but has not reached
zero. There is evidence linking KS to a herpesvirus
(herpesvirus 8 [HHV-8], also called
KS-associated
herpes virus
[KSHV]).
68
The virus is readily transmit-
ted through homosexual and heterosexual activities;
however, there is a disproportionately higher inci-
dence of KS in men who have sex with men com-
pared with women and other men. Maternal–infant
transmission also can rarely occur. The virus has been
detected in saliva from infected persons, and other
nonsexual modes of transmission are suspected.
The lesions of KS can be found on the skin and on
any mucosal surface in the oral cavity, gastrointestinal
tract, and lungs. More than 50% of people with skin
lesions also have gastrointestinal lesions. The disease
usually begins as one or more macules, papules, or
violet skin lesions that enlarge and become darker
(Fig. 16-11). Tumor nodules frequently are located
on the trunk, neck, and head, especially the tip of the
nose. They usually are painless in the early stages, but
discomfort may occur as the tumor develops. Invasion
of internal organs, including the lungs, gastrointes-
tinal tract, and lymphatic system, commonly occurs.
Gastrointestinal tract KS is often asymptomatic,
but can cause pain, bleeding, or obstruction.
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