What is the definition or description of: pneumocystis pneumonia?

Infection of lung: An organism called pneumocystis carini (now jirovechi) can cause infection of the lung, esp in the immunocompromised hosts and can cause profound hypoxemia, but is easily treated with good old septran.

From a certain germ: Pneumonia can be caused by several different types of germs when they get into the lungs. The body usually fights them as a "foreign invader". Some germs are very common, living in our mouths or on our skin and rarely causing an infection. Others are always dangerous. Pneumocystis is a partcular germ that is around us a lot, but causes infection only if the body's immune defenses aren't working.