- Important cause of pneumonia in humans associated with immunodeficiency states
- It has been occasionally reported in young or immunosuppressed animals (e.g. Arabian foals with congenital immunodeficiency)
- Grossly:
- Histologically:
- Alveoli are filled with pale staining acidophilic material (= trophozoite and cyst forms of the organism)
- It is thought that as P. carinii is often present as a latent infection, alveolar macrophages normally control the organism - a process which fails in immunodeficient states