Cryptococcosis is an infection caused by inhaling the fungus Cryptococcus neoformans. It is one of the diseases most often affecting AIDS patients. Cryptococcosis may be limited to the lungs, but frequently spreads throughout the body. Although almost any organ can be infected, the fungus is often fatal if it infects the nervous system, where it causes inflammation of the membranes covering the brain and spinal cord (meningitis).

The fungus causing cryptococcus, C. neoformans, is found in soil contaminated with pigeon or other bird droppings. It has also been found on unwashed raw fruit. Cryptococcosis is rare in healthy individuals, but is the most common fungal infection affecting people with AIDS.

People with Hodgkin's disease or who are taking large doses of drugs that suppress the immune system (corticosteroids, chemotherapy drugs) are more susceptible to cryptococcal infection.

Once the cryptococcal fungus reaches the lungs, three things can happen. The...