Definition of Pneumocystis jiroveci pneumonia:

Pneumocystis jiroveci pneumonia is a fungal infection of the lungs. The disease used to be called Pneumocystis carinii.

Causes, incidence, and risk factors:

This type of pneumonia is caused by the fungus Pneumocystis jiroveci. This fungus is common in the environment and does not cause illness in healthy people.

However, it can cause a lung infection in people with a weakened immune system due to:

• Cancer
• Chronic use of corticosteroids or other medications that weaken the immune system
• HIV/AIDS
• Organ or bone marrow transplant

Pneumocystis jiroveci was a relatively rare infection before the AIDS epidemic. Before the use of preventive antibiotics for the condition, most people in the United States with advanced AIDS would develop it.