This 46-year-old male presented with a complaint of right-sided chest pain of six months duration. Chest x-ray showed a nodular mass in the lower lobe of the right lung. The mass was resected surgically.
The 3.5 x 2.5-cm mass was firm, gray, and gelatinous. The mass proved to be a cryptococcal lesion.
Cryptococcus neoformans is present in the soil and in bird (particularly pigeon) droppings.
The organism infects humans when it is inhaled.
Normal healthy people can get cryptococcal meningoencephalitis but cryptococcal infections are more common in individuals
(1) who receive high-dose corticosteroids and/or
(2) who have AIDS, leukemia, lymphoma, systemic lupus erythematosus,
Hodgkin’s disease, sarcoidosis, or transplant patients.
Three properties of Cryptococcus neoformans are associated with virulence:
(1) the capsular polysaccharide;
(2) resistance to killing by alveolar macrophages; and (3) production of phenoloxidase an enzyme that consumes host epinephrine in the synthesis of fungal melanin and thus protects the fungi from the epinephrine oxidative system present in the host nervous system.
It is thought that one reason why Cryptococcus neoformans preferentially infects the brain may be because the CSF lacks alternative pathway complement components (present in serum) that bind to the carbohydrate capsule and facilitate phagocytosis and killing by polymorphonuclear cells.
- Rooney PJ, Klein BS. Linking fungal morphogenesis with virulence. Cell Microbiol 2002 Mar;4(3):127-37.
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