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 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)

The main treatment for PCP is with drugs that kill the bacteria (antimicrobial therapy). Antibiotics can be given by mouth (orally) or through a vein (intravenous), depending on the severity of the illness.

People with low oxygen levels and moderate to severe PCP often take corticosteroids as well.

Pneumocystis carinii pneumonia can be life-threatening, and respiratory failure can lead to death. People with this condition need early and effective treatment. For moderate to severe PCP in people with AIDS, the use of corticosteroids has decreased mortality.

• Pleural effusion (extremely rare)
• Pneumothorax
• Respiratory failure (may require mechanical ventilation)

If you have a weakened immune system due to AIDS, cancer, transplantation, or corticosteroid use, call your doctor if you develop a cough, fever, or shortness of breath.

While many infections can lead to similar symptoms, you should have a medical evaluation to rule out opportunistic infections such as PCP.

Preventive therapy is recommended for:

• AIDS patients with CD4 counts below 200
• People on chronic high-dose corticosteroids
• People who have had previous episodes of PCP