Pneumocystis pneumonia 1

Pneumocystis pneumonia

Pneumocystis jirovecii pneumoniaClassification and external resources

Pneumocystis jirovecii cysts from bronchoalveolar lavage, stained with Toluidin blue O stain

ICD-10 B20.6 [1]

ICD-9 136.3 [2]

DiseasesDB 10160 [3]

MedlinePlus 000671 [4]

eMedicine med/1850 [5]

MeSH D011020 [6]

Pneumocystis pneumonia (PCP) or pneumocystosis is a form of pneumonia, caused by the yeast-like fungus(which had previously been erroneously classified as a protozoan) Pneumocystis jirovecii.Pneumocystis is commonly found in the lungs of healthy people, but, being a source of opportunistic infection, it cancause a lung infection in people with a weak immune system. Pneumocystis pneumonia is especially seen in peoplewith cancer[citation needed], HIV/AIDS and the use of medications that affect the immune system.

Signs and symptomsSymptoms of PCP include fever, non-productive cough (because sputum is too viscous to become productive),shortness of breath (especially on exertion), weight loss, and night sweats. There is usually not a large amount ofsputum 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.Pneumothorax is a well-known complication of PCP. An acute history of chest pain with breathlessness anddiminished breath sounds is typical of pneumothorax.[citation needed]

Disease courseThe risk of PCP increases when CD4 positive cell levels are less than 200 cells/μL. In these immunosuppressedindividuals the manifestations of the infection are highly variable. The disease attacks the interstitial, fibrous tissueof the lungs, with marked thickening of the alveolar septa and alveoli, leading to significant hypoxia which can befatal if not treated aggressively. In this situation LDH levels increase and gas exchange is compromised. Oxygen isless able to diffuse into the blood, leading to hypoxia. Hypoxia, along with high arterial carbon dioxide (CO2) levels,stimulates hyper-ventilatory effort, thereby causing dyspnea (breathlessness).

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Diagnosis

X-ray of Pneumocystis jirovecii pneumonia.There is increased opacification (whiteness) inthe lower lungs on both sides, characteristic of

Pneumocystis pneumonia

The diagnosis can be confirmed by the characteristic appearance of thechest x-ray, which shows widespread pulmonary infiltrates, and anarterial oxygen level (PaO2) that is strikingly lower than would beexpected from symptoms. Gallium 67 scans are also useful in thediagnosis. They are abnormal in approximately 90% of cases and areoften positive before the chest x-ray becomes abnormal. The diagnosiscan be definitively confirmed by histological identification of thecausative organism in sputum or bronchio-alveolar lavage (lung rinse).Staining with toluidine blue, silver stain, periodic-acid schiff stain, oran immunofluorescence assay will show the characteristic cysts. Thecysts resemble crushed ping-pong balls and are present in aggregatesof 2 to 8 (and not to be confused with Histoplasma or Cryptococcus,which typically do not form aggregates of spores or cells). A lungbiopsy would show thickened alveolar septa with fluffy eosinophilicexudate in the alveoli. Both the thickened septa and the fluffy exudatecontribute to dysfunctional diffusion capacity which is characteristic ofthis pneumonia.

Pneumocystis infection can also be diagnosed by immunofluorescent orhistochemical staining of the specimen, and more recently bymolecular analysis of polymerase chain reaction products comparingDNA samples. Notably, simple molecular detection of Pneumocystis jirovecii in lung fluids does not mean that aperson has Pneumocystis pneumonia or infection by HIV. The fungus appears to be present in healthy individuals inthe general population.

Prevention and treatmentIn immunocompromised patients, prophylaxis with co-trimoxazole (trimethoprim/sulfamethoxazole), atovaquone, orregular pentamidine inhalations may help prevent PCP.Antipneumocystic medication is used with concomitant steroids in order to avoid inflammation, which causes anexacerbation of symptoms about four days after treatment begins if steroids are not used. By far the most commonlyused medication is trimethoprim/sulfamethoxazole, but some patients are unable to tolerate this treatment due toallergies. Other medications that are used, alone or in combination, include pentamidine, trimetrexate, dapsone,atovaquone, primaquine, pafuramidine maleate (under investigation), and clindamycin. Treatment is usually for aperiod of about 21 days.Pentamidine is less often used as its major limitation is the high frequency of side effects. These include acutepancreatitis, renal failure, hepatotoxicity, leukopenia, rash, fever, and hypoglycaemia.

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Epidemiology

Pneumocystis jirovecii

The disease PCP is relatively rare in people with normal immunesystems, but common among people with weakened immune systems,such as premature or severely malnourished children, the elderly, andespecially persons living with HIV/AIDS (in whom it is mostcommonly observed). PCP can also develop in patients who are takingimmunosuppressive medications. It can occur in patients who haveundergone solid organ transplantation or bone marrow transplantationand after surgery. Infections with Pneumocystis pneumonia are alsocommon in infants with hyper IgM syndrome, an X-linked orautosomal recessive trait.

The causative organism of PCP is distributed worldwide and Pneumocystis pneumonia has been described in allcontinents except Antarctica. Greater than 75% of children are seropositive by the age of 4, which suggest a highbackground exposure to the organism. A post-mortem study conducted in Chile of 96 persons who died of unrelatedcauses (suicide, traffic accidents, and so forth) found that 65 (68%) of them had pneumocystis in their lungs, whichsuggests that asymptomatic pneumocystis infection is extremely common.

Pneumocystis jirovecii was originally described as a rare cause of pneumonia in neonates. It is commonly believed tobe a commensal organism (dependent upon its human host for survival). The possibility of person-to-persontransmission has recently gained credence, with supporting evidence coming from many different genotyping studiesof Pneumocystis jirovecii isolates from human lung tissue. For example, in one outbreak of 12 cases amongtransplant patients in Leiden, it was suggested as likely, but not proven, that human-to-human spread may haveoccurred.

PCP and AIDSSince the start of the AIDS epidemic, PCP has been closely associated with AIDS. Because it only occurs in animmunocompromised host, it may be the first clue to a new AIDS diagnosis if the patient has no other reason to beimmunocompromised (e.g. taking immunosuppressive drugs for organ transplant). An unusual rise in the number ofPCP cases in North America, noticed when physicians began requesting large quantities of the rarely used antibioticpentamidine, was the first clue to the existence of AIDS in the early 1980s.Prior to the development of more effective treatments, PCP was a common and rapid cause of death in persons livingwith AIDS. Much of the incidence of PCP has been reduced by instituting a standard practice of using oralco-trimoxazole to prevent the disease in people with CD4 counts less than 200/μL. In populations that do not haveaccess to preventive treatment, PCP continues to be a major cause of death in AIDS [citation needed].

NomenclatureThe older name Pneumocystis carinii (which now only applies to the Pneumocystis species that is found in rats) isstill in common usage. As a result, Pneumocystis pneumonia (PCP) is also known as Pneumocystis jiroveci[i]pneumonia and (incorrectly) as Pneumocystis carinii pneumonia.Regarding nomenclature, when the name of Pneumocystis pneumonia (PCP) changed from P. carinii pneumonia toP. jirovecii pneumonia, it was at first felt that "PJP" should replace "PCP". However, because the term PCP wasalready used among physicians that managed patients with Pneumocystis infection, it was rationalized that the termPCP could continue to be used, as it stood for PneumoCystis (jirovecii) Pneumonia.[citation needed]

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References[1] http:/ / apps. who. int/ classifications/ icd10/ browse/ 2010/ en#/ B20. 6[2] http:/ / www. icd9data. com/ getICD9Code. ashx?icd9=136. 3[3] http:/ / www. diseasesdatabase. com/ ddb10160. htm[4] http:/ / www. nlm. nih. gov/ medlineplus/ ency/ article/ 000671. htm[5] http:/ / www. emedicine. com/ med/ topic1850. htm[6] http:/ / www. nlm. nih. gov/ cgi/ mesh/ 2014/ MB_cgi?field=uid& term=D011020

Article Sources and Contributors 5

Article Sources and ContributorsPneumocystis pneumonia  Source: http://en.wikipedia.org/w/index.php?oldid=592819123  Contributors: ARMDCM, Akc203, Andrew Benton, Anrnusna, Anupam, Arcadian, Bachrach44,Brighterorange, Broken rusk, C6541, Chakradiwaker, Cionar, Claireislovely, DBigXray, Diberri, Dysmorodrepanis, Edgar181, Edward321, Egoviri, Fallon Turner, Fangjian, Fvasconcellos, Gak,George Ho, Gilliam, Gor n bein, GrahamColm, Heliocybe, Hovea, Hower64, InsufficientData, JamesAM, Jmarchn, Jmh649, Joe Decker, JoeSmack, JulianLav, Kbdank71, M malligan,Mattgalarneau, Maxim, MazinX, Medic2008, MidgeMcEwan, Mikejones2255, Mimihitam, Mistyfied, Moldekarl, MoogleDan, Moonraker12, MuanN, Mukake, Navyls, Nnemo, Onco p53,Orlandoturner, OwenBlacker, Pblaauw, Pete.Hurd, ProfessorAM, RDBrown, Rich Farmbrough, Rjwilmsi, Roksonarim, Sesamehoneytart, Stepshep, Thingg, Tim1357, Tony1, Tristynu, VBalian,Wickey-nl, Xmp, 82 anonymous edits

Image Sources, Licenses and ContributorsFile:Pneumocystis.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Pneumocystis.jpg  License: Public Domain  Contributors: User InvictaHOG on en.wikipediaFile:PCPxray.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:PCPxray.jpg  License: Public Domain  Contributors: User InvictaHOG on en.wikipediaFile:Pneumocystisjiroveci.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Pneumocystisjiroveci.jpg  License: Creative Commons Attribution-Sharealike 2.0  Contributors: PulminaryPathology

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