Cryptococcosis

Cryptococcosis is an infection acquired by inhalation of soil contaminated with the encapsulated yeast (fungus) Cryptococcus neoformans.

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Etiology and Incidence

Cryptococcosis is a defining opportunistic infection for AIDS, although patients with Hodgkin's or other lymphomas or sarcoidosis or those receiving long-term corticosteroid therapy are also at increased risk.

Distribution is worldwide. The prevalence of cryptococcosis has been increasing over the past 20 years for many reasons, including the increase in indicence of AIDS and the expanded use of immunosuppressive drugs.

In humans, C. neoformans causes three types of infections:

• Wound or cutaneous cryptococcosis
• Pulmonary cryptococcosis, and
• Cryptococcal meningitis.

Cryptococcal meningitis (infection of the brain) is believed to result from dissemination of the fungus from either an observed or unappreciated pulmonary infection. Cryptococcus gattii causes infections in immunocompetent people (those having a functioning immune system), but C. neoformans v. grubii, and v. neoformans usually only cause clinically evident infections in persons who have some form of defect in their immune systems (immunocompromised persons). People who have defects in their cell-mediated immunity, for example, people with AIDS, are especially susceptible to disseminated cryptococcosis. Cryptococcosis is often fatal, especially if untreated.

Diagnosis

Symptoms include chest pain, dry cough, swelling of abdomen, headache, blurred vision and confusion. Symptoms may not be able to be detected.

Detection of cryptococcal antigen (capsular material) by culture of CSF, sputum and urine provides definitive diagnosis. Blood cultures may be positive in heavy infections.

Treatment

The standard regimen of treatment in non-AIDS patients intravenous Amphotericin B combined with oral flucytosine.

AIDS patients often have a reduced response to Amphotericin B and flucytosine, therefore after initial treatment as above, oral fluconazole can be used.