Lung, Pneumocystis jirovecii

Pneumocystis jirovecii is a eukaryotic microorganism that is the human-specific counterpart of Pneumocystis carinii (which is found in a wide range of animals). It is a ubiquitous fungus that causes opportunistic disease. A member of ascomycetous fungi, it is 1-4 µm in the asexual trophic form and 8 µm in the sexually reproductive cystic forms. It is often associated with HIV infection, and immunodeficiencies. Patients usually present with dyspnea, dry cough, and fever.

The BAL shows basophilic foamy or "fluffy" proteinaceous material with occasional scattered round-shaped cysts with nuclei adjacent to the cell wall.

See LMP62282 - Lung, Pneumocystis jirovecii pneumonia for histologic section from a different case (link in related content).