Page 113 - AIDSBK23C

Page 113

COCCIDIOIDES IMMITIS INFECTIONS

Coccidioidomycosis is included in the definitional criteria for AIDS because it may
appear in HIV-infected persons who have lived in endemic areas--arid plains of the
Southwestern United States, Mexico, and Central and South America.[392] C immitis exists in a
mycelial form (septated alternating arthrospores) in soils and is released into the air as
arthroconidia that are inhaled.[454] C immitis grows as a yeast form in tissues. In areas endemic
for C immitis, HIV-infected persons may prevent infection by avoiding exposure to dusty
environments or areas where soil is disturbed.[208] Coccidioidomycosis in AIDS probably
represents a reactivation of a previous infection rather than recent infection.[483]
Coccidioidomycosis in association with AIDS tends to be a widely disseminated
infection involving numerous organs (Table 5). The lung serves as the portal of entry for
Coccidioides immitis . There are several clinical patterns of involvement, including focal
pulmonary disease, diffuse pulmonary disease, cutaneous disease, meningitis, and wide
dissemination. Grossly visible granulomas similar to other dimorphic fungi and to
Mycobacterium tuberculosis may be present in lung, but often are not seen in other organs.
Serologic tests for antibody to C immitis are positive in about two thirds of cases.[454,483]
Widespread use of antiretroviral therapy decreases the incidence and the severity of
coccidioidomycosis.[484]
The most frequent symptoms are fever with chills, weight loss, and night sweats. The
clinical presentation is most often as pulmonary disease in 80%, followed by meningitis in 15%
of cases. A fourth of patients have lymphadenopathy. A chest radiograph will demonstrate a
diffuse reticulonodular infiltrate in over half of cases, but negative findings may occur in 16% of
cases.[483] Diagnosis can be made by several methods. In general, skin testing is not useful,
since few HIV-infected persons with coccidioidomycosis will have a positive result. Most of the
false negative serologic tests are found when diffuse pulmonary disease is present. Blood
cultures will be positive in about 12% of cases. Cultures of cerebrospinal fluid are positive in
over half of cases of C immitis meningitis.[454]
Microscopic diagnosis is made by finding clusters of large 10 to 80 micron thick-walled
spherules containing endospores in tissue biopsies. Spherules may also be identified in sputum
and bronchoalveolar lavage fluid. Ruptured spherules may be partially collapsed with small 2 to
5 micron endospores close by. Once the endospores are released, they begin to grow into
spherules with endospores, completing the life cycle. Thus, variably sized spherules are often
present and only the larger ones will have well-defined endospores. Both Gomori methenamine
silver (GMS) and periodic acid-Schiff (PAS) stains are helpful in identifying the organisms. An
inflammatory reaction accompanying C immitis spherules tends to be quite sparse, consisting of
only scattered lymphocytes, neutrophils, and macrophages.
Treatment with amphotericin B may be useful for acute and/or chronic infections.
Secondary prophylaxis with itraconazole, fluconazole, or ketoconazole may be employed. Death
occurs from coccidioidomycosis in two thirds of patients who have C immitis infection at
autopsy. The mortality rate is highest when diffuse pulmonary disease is present and/or the CD4
lymphocyte count is <50/µL. One important etiologic differential diagnosis in disseminated
coccidioidomycosis should be made: a disseminated form of this infection can also occur in
anabolic steroid abusers or corticosteroid users, who may also be young males. Thus, testing to
confirm or exclude HIV status is essential.[396,483]