Pneumocystis pneumonia
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Overview
Pneumocystis pneumonia (PCP) is a form of pneumonia caused by the yeast-like fungal Pneumocystis jirovecii (Jirovecii is pronounced "yee row vet zee eye"). The causal agent was originally described as a protozoan and spelled P. jiroveci and prior to then was classified as a form of Pneumocystis carinii, a name still in common usage.[1][2] These names are discussed below. As a result, Pneumocystis pneumonia (PCP) has also been known as Pneumocystis jiroveci[i] pneumonia and as Pneumocystis carinii pneumonia, as is also explained below.[3][4][5]
It is relatively rare in people with normal immune systems but common among people with weakened immune systems, such as premature or severely malnourished children, the elderly, and especially AIDS patients, in whom it is most commonly observed today.[6] PCP can also develop in patients who are taking immunosuppressant medications (e.g. patients who have undergone solid organ transplantation) and in patients who have undergone bone marrow transplantation.
The organism is distributed worldwide[7][2].
Epidemiology
Pneumocystis pneumonia has been described in all continents except Antarctica.[7] It was originally described as a rare cause of pneumonia in neonates. It is believed to be an environmental organism, and human-to-human transmission is thought not to occur (although in one outbreak of 12 cases among transplant patients in Leiden it was postulated, but not proven, that human-to-human spread may have occurred).[8] Greater than 75% of children are seropositive by the age of 4, which suggest a high background exposure to the organism.
Since the start of the HIV pandemic, PCP has been closely associated with AIDS. Because it only occurs in an immunocompromised host, it may be the first clue to a new AIDS diagnosis if the patient has no other reason to be immunocompromised (e.g. taking immunosuppressive drugs for organ transplant). An unusual rise in the number of PCP cases in North America, noticed when physicians began requesting large quantities of the rarely used antibiotic pentamidine, was the first clue to the existence of AIDS in the early 1980s.[9][10]
Prior to the development of more effective treatments, PCP was a common and rapid cause of death in persons living with AIDS. Much of the incidence of PCP has been reduced by instituting a standard practice of using oral co-trimoxazole to prevent the disease in people with CD4 counts less than 200/mm³. In populations that do not have access to preventative treatment, PCP continues to be a major cause of death in AIDS.
In immunocompromised patients (e.g. cancer patients on chemotherapy, or persons living with AIDS with a CD4+ T-cell count below 200/μl), prophylaxis with regular pentamidine inhalations or sulfamethoxazole/trimethoprim (co-trimoxazole or TMP-SMX) may be necessary to prevent PCP.
Symptoms
Symptoms of PCP include fever, non-productive cough, shortness of breath (especially on exertion), weight loss and night sweats. There is usually not a large amount of sputum with PCP unless the patient has an additional bacterial infection. The fungus can invade other visceral organs, such as the liver, spleen and kidney, but only in a minority of cases.
Pathophysiology
Diagnosis
The diagnosis can be confirmed by the characteristic appearance of the chest x-ray which shows widespread pulmonary infiltrates, and an arterial oxygen level (pO2) strikingly lower than would be expected from symptoms. The diagnosis can be definitively confirmed by pathologic identification of the causative organism in induced sputum or bronchial washings obtained by bronchoscopy with coloration by toluidine blue or immunofluorescence assay, which will show characteristic cysts [3].
Pneumocystis infection can also be diagnosed by immunofluorescent or histochemical staining of the specimen, and more recently by molecular analysis of PCR products comparing DNA samples. Notably, simple molecular detection of Pneumocystis jirovecii in lung fluids does not mean that a person has Pneumocystis pneumonia or infection by HIV. The fungus appears to be present in healthy individuals also in the general population.[11]
Life-cycle
Treatment
Guidelines
To read about guidelines for prevention and treatment of Pneumocystis pneumonia Infections in HIV-Infected Adults and Adolescents, click here.
References
- ↑ Stringer JR, Beard CB, Miller RF, Wakefield AE (2002). "A new name (Pneumocystis jiroveci) for Pneumocystis from humans". Emerg Infect Dis. 8 (9): 891–6. PMID 12194762.
- ↑ Redhead SA, Cushion MT, Frenkel JK, Stringer JR (2006). "Pneumocystis and Trypanosoma cruzi: nomenclature and typifications". J Eukaryot Microbiol. 53 (1): 2–11. PMID 16441572.
- ↑ Cushion MT . (1998). "Chapter 34. Pneumocystis carinii. In: Collier, L., Balows, A. & Sussman, M. (ed.), Topley and Wilson's Microbiology and Microbial Infections 9th ed. Arnold and Oxford Press, New York": 645–683.
- ↑ Cushion MT (1998). "Taxonomy, genetic organization, and life cycle of Pneumocystis carinii". Semin. Respir. Infect. 13 (4): 304–312.
- ↑ Cushion MT (2004). "Pneumocystis: unraveling the cloak of obscurity". Trends Microbiol. 12 (5): 243–249.
- ↑ Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed. ed.). McGraw Hill. ISBN 0838585299.
- ↑ 7.0 7.1 Morris A; et al. (2004). "Current Epidemiology of Pneumocystis Pneumonia". Emerg Infect Dis. 10 (10): 1713–1720. PMID 15504255.
- ↑ de Boer M, Bruijnesteijn van Coppenraet L, Gaasbeek A; et al. (2007). "An outbreak of Pneumocystis jiroveci pneumonia with 1 predominant genotype
among renal transplant recipients: interhuman transmission or a common environmental source?". Clin Infect Dis. 44 (9): 1143&ndash, 49. PMID 17407029. line feed character in
|title=at position 79 (help) - ↑ Fannin S, Gottlieb MS, Weisman JD; et al. (1982). "A Cluster of Kaposi's Sarcoma and Pneumocystis carinii pneumonia among homosexual male residents of Los Angeles and Range Counties, California". MMWR Weekly. 31 (32): 305&ndash, 7.
- ↑ Masur H, Michelis MA, Greene JB; et al. (1981). "An outbreak of community-acquired Pneumocystis carinii pneumonia". N Engl J Med. 305: 1431–8.
- ↑ Medrano FJ; et al. (2005). "Pneumocystis jirovecii in General Population". Emerg Infect Dis. 11 (2): 245–250. PMID 15752442.