Page 121 - AIDSBK23C

Page 121

prominent obliterative angiitis. The amastigote forms of T cruzi can be present within glial cells,
macrophages, and endothelial cells. Myocardial involvement with acute and/or chronic
myocarditis may also be present.[521]

PARACOCCIDIOIDOMYCOSIS.-- The dimorphic fungus Paracoccidioides
brasiliensis is endemic to South America, where it is found in the mycelial form in soil. It is
acquired as an infection by inhalation of mycelial conidia. In tissues there is granulomatous
inflammation in which the yeast cells have a double membrane and multiple budding forming a
"steering wheel" shape. Estrogen in women past puberty has a protective effect in preventing
transformation to the invasive yeast form of this fungus. Infected persons may become
asymptomatic carriers. The acute or subacute form is more common among children and young
adults, and manifested by generalized lymphadenopathy and hematogenous dissemination with
hepatosplenomegaly, skin, intestinal, and bone lesions. Adults more than 30 years of age
typically have the chronic form, which manifests as pulmonary lesions, often associated with
ulcerations in the oral, nasal, or laryngeal mucosa, as well as skin and visceral lesions.[522,523]
Persons infected with HIV are more likely to have reactivation of an infection with P
brasiliensis, rather than a new infection. Such persons are less likely to have a history of living
in rural areas or working in agriculture than non-HIV infected persons. The CD4 lymphocyte
count is typically below 200/µL. The incidence of co-infection with HIV and P brasiliensis is
estimated to be 1.4%. Such co-infections are more likely to predict rapid progression of
disease.[524]
HIV infected persons are likely to develop a form of the disease that has elements of both
acute and chronic paracoccidioidomycosis. In particular, they are more likely than HIV negative
persons to develop cutaneous lesions, particularly ulcerated papular lesions that may have a
necrotic center. Lymph nodes are most often involved, followed by respiratory tract, with
pulmonary interstitial infiltrates. Ulcerated oral lesions can be present as well. Seronegativity
for the fungus occurs in about half of cases, making identification of the yeast in tissue biopsies
and sputum samples the best diagnostic method. Tissue involvement is characterized by poorly
formed granulomas with prominent necrosis and numerous yeasts. Serologic testing may aid in
diagnosis.[524,525]
Amphotericin B appears to be the most efficacious pharmacologic therapy for infections
with acute features, while itraconazole may have usefulness in more chronic forms of this
disease. The prevalence of P brasiliensis in HIV infected persons may be lower than expected
because the use of trimethoprim-sulfamethoxazole as prophylaxis against Pneumocystis
pneumonia is also effective against paracoccidioidomycosis.[525]

STRONGYLOIDIASIS.-- The parasite Strongyloides stercoralis has a worldwide
distribution and is transmitted when infective larvae in contaminated soil penetrate the skin, but
fecal-oral and sexual transmission are also possible. In immunocompromised hosts, it is possible
for an uncontrolled autoinfection cycle to occur in which rhabditiform larvae in the intestine molt
into filariform larvae that invade the intestinal wall and disseminate, producing a hyperinfection
syndrome called disseminated strongyloidiasis which has high morbidity and mortality. The
most frequent sites of involvement are the gastrointestinal tract, respiratory tract, skin, and
central nervous system. The enteropathy that can occur with HIV infection may predispose to
strongyloidiasis. Clinical findings include fever, cachexia, diarrhea, melena, abdominal pain,
cough, and dyspnea. A complication is sepsis with enteric organisms. Mesenteric lymph node