Lung
Infectious
Fungal
Pneumocystis
Author: Elliot Weisenberg, M.D.
Last author update: 1 September 2011
Last staff update: 26 July 2023 (update in progress)
Copyright: 2003-2023, PathologyOutlines.com, Inc.
PubMed search: Pneumocystis jirovecii [title] pneumonia pulmonary
Table of Contents
Clinical features | Diagrams / tables | Diagnosis | Treatment | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Differential diagnosisCite this page: Weisenberg E. Pneumocystis. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/lungnontumorPCP.html. Accessed September 22nd, 2023.
Clinical features
- Formerly known (incorrectly) as P. carinii, a pneumocystis variant that occurs in animals; P. jiroveci1 is specific to humans (eMedicine)
- Opportunistic yeast-like fungus present in bronchoalveolar lavage (BAL), sputum or biopsy
- Most common pneumonia in AIDS patients, who are at high risk if CD4 < 200 or if protein-calorie malnutrition
- May also occur in otherwise immunocompetent patients with protein-calorie malnutrition, hematologic malignancies or undergoing chemotherapy or chronic corticosteroid treatment
- Causes diffuse or patchy pneumonia; may have coexisting CMV or other infections
- Incidence has declined dramatically in HIV patients, but is increasing in other immunosuppressed patients, who have 24% mortality at 30 days (BMC Infect Dis 2011;11:76)
- Radiology: usually atypical interstitial pneumonia; lung biopsy is rarely required for diagnosis
Diagrams / tables
Images hosted on other servers:
Life cycle
Diagnosis
- Bronchoalveolar lavage and imprints have high sensitivity (Arch Pathol Lab Med 2007;131:1582)
- However, PCR plus expectorated or induced sputum is more cost effective options than BAL or chest xray alone (PLoS One 2011;6:e23158)
- Also immunofluorescence
Treatment
- Pentamidine, folic acid inhibitors (especially sulfonamides) and anti-HIV drugs
- Prophylactic therapy is currently routine in the setting of HIV and in combination with HAART treatment
Microscopic (histologic) description
- Alveolar spaces filled with pink, foamy amorphous material composed of proliferating fungi and cell debris
- Fungi are 4 - 6 microns, cup / boat shaped cysts
- Also mild inflammatory reaction with fibrin exudate, hyaline membranes
- Solitary necrotizing granulomas and miliary disease are also described; granulomatous cases lack classic features of intra-alveolar foamy exudates with pneumocystis (Am J Surg Pathol 2010;34:730)
Microscopic (histologic) images
Images hosted on other servers:
Cup shaped organisms
GMS stain
Polychrome methylene blue stain
Positive stains
- GMS, Warthin-Starry, other silver stains and Gram-Weigert
Differential diagnosis
- Alveolar proteinosis: diffuse pulmonary opacification and intra-alveolar PAS positive material and lipid; exudative pulmonary edema, sputum contains gelatinous material; no inflammation; alveolar contents contain type II pneumocytes and necrotic alveolar macrophages
- Goodpasture syndrome: necrotizing, hemorrhagic, interstitial pneumonitis; associated with rapidly proliferative glomerulonephritis, linear immunoglobulin deposits on basement membranes of alveolar septal walls; also intra-alveolar hemorrhage, septal thickening and hypertrophy, organization of blood in alveolar spaces
- BOOP: bronchiolar and alveolar plugs of loose fibrous tissue
