Cryptococcus neoformans: A fungus that occurs worldwide and is mainly found in debris around pigeon roosts and soil contaminated with decaying pigeon or chicken droppings. The infection is acquired by inhalation, and those infected may display a range of symptoms ranging from colonization of the airways without any symptoms to severe pneumonia. Spread to the brain may occur, causing meningoencephalitis that is fatal if untreated. C. neoformans most commonly affects those with a weakened immune system although those with normal immune function can also be infected. Although infection in the general population is rare, approximately 7%-15% of patients with AIDS develop cryptococcal infections (cryptococcosis). Amphotericin B and other antifungal medications are used to treat cryptococcal infections.
