Pneumocystis jirovecii pneumonia causes

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