Noun
pneumocystis
(pathology) A parasitic fungal organism of the genus Pneumocystis, in humans specifically Pneumocystis jorevicii.
Confusion between the two pathogens' life-cycles led him to briefly recognize his genus Schizotrypanum, but following the description of Pneumocystis by others as an independent genus, Chagas returned to the use of the name Trypanosoma cruzi. Source: Internet
However, if the immune system is damaged they can be life-threatening; for instance, Pneumocystis jirovecii is responsible for severe lung infections that occur in AIDS patients. Source: Internet