Cryptococcus neoformans, a type of microscopic yeast that is found worldwide, can cause pulmonary infections that can potentially spread to other areas of the body. This infection is called cryptococcosis. Individuals who are immunocompromised, especially HIV/AIDS patients, are more susceptible to developing the infection.
Most infections develop after the yeast is inhaled into the lungs. Cryptococci have large polysaccharide (sugar) capsules that strongly resist phagocytosis. This means the body's immune system cells have to work hard to engulf the yeast organism.
The body's inflammatory reaction to the inhaled yeast causes a primary pulmonary-lymph node complex, which usually prevents the organism from spreading beyond the lungs. Most pulmonary infections are asymptomatic (cause no symptoms), but patients who are severely immunocompromised may develop diffuse interstitial pneumonitis (inflammation of the lungs).
C. neoformans can spread beyond the lungs, especially if the patient is immunocompromised. Dissemination (spread to other body parts) can occur during the initial stage of the infection or during reactivation of infection years later.
The most common site involved is the central nervous system (CNS, brain and spinal cord). Most patients with CNS infections suffer from altered mental states, behavioral changes, headache and fever. Focal (localized) neurologic signs are unusual.
The typical pathologic findings of CNS cryptococcosis include meningitis (infection and inflammation of the membranes that surround the brain and spinal cord), cryptococcomas (infectious inflammatory lesions, typically in the brain, but also found in the lung and elsewhere) and dilated spaces near blood vessels. Patients who have AIDS and cryptococcal meningitis account for more than 80% of the patients with cryptococcosis.
Significant differences are reported in the inflammatory response to cryptococcal meningoencephalitis (inflammation of the brain, spinal cord and meninges) among patients who have HIV/AIDS and those who do not have HIV/AIDS. Granulomatous inflammation (lumps formed from an accumulation of inflammatory cells) is not common in AIDS patients, while most patients without HIV/AIDS have granulomas.
If left untreated, cryptococcal meningitis results in death 100% of the time. Therefore, early diagnosis and treatment with amphotericin B is essential. Prior to the discovery of amphotericin B in 1955, 80% of patients with CNS involvement died within two years of diagnosis.
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