Definition of Pneumocystis carinii pneumonia:

Pneumocystis carinii pneumonia (PCP) is a fungal infection of the lungs.

Causes, incidence, and risk factors:

PCP is a pneumonia caused by the fungal organism Pneumocystis carinii (now renamed Pneumocystis jiroveci). This organism is common in the environment and does not cause illness in healthy people.

However, Pneumocystis carinii can cause a lung infection in in people with a weakened immune system due to any of the following conditions:

• Cancer
• Chronic use of corticosteroids or other medications that affect the immune system
• HIV/AIDS
• Solid organ or bone marrow transplant

PCP was a relatively rare infection before the AIDS epidemic. Before the use of preventive antibiotics for PCP, up to 70% of people in the U.S. with advanced AIDS would develop PCP.