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

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 and/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.

PCP in those with AIDS usually develops slowly and is less severe. People with PCP who do not have AIDS usually get sick faster and are more acutely ill.

Symptoms include:

• Cough -- often mild and dry
• Fever
• Rapid breathing
• Shortness of breath -- especially with activity (exertion)

• Blood gases
• Bronchoscopy (with lavage)
• Lung biopsy
• X-ray of the chest
• Sputum induction (to detect Pneumocystis carinii)