Pneumocystis jiroveci pneumonia

Pneumocystis jiroveci pneumonia or Pneumocystis pneumonia (PCP) is a form of pneumonia caused by a yeast-like fungal microorganism called Pneumocystis jiroveci (sometimes spelled jirovecii, formerly known as Pneumocystis carinii). It is relatively rare in people with normal immune systems but common among people with AIDS. PCP can also develop in patients who are taking immunosuppressant medications (e.g., patients who have undergone solid organ transplantion) and in patients who have undergone bone marrow transplantation. more...

Symptoms

Symptoms of PCP include high 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.

Diagnosis

The clinical 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.

PCP and AIDS

Because PCP rarely occurs without AIDS, it can be one of the first clues to a new AIDS diagnosis, though it does not generally occur unless the CD4 count is less than 200/mm³. An unusual rise in 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.

Prior to the development of more effective treatments, PCP was a common and rapid cause of death in AIDS patients. Much of the incidence of PCP has been reduced by instituting a standard practice of using oral trimethoprim/sulfamethoxazole 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.

Treatments

Antipneumocystic medication is used with concomitant steroids in order to avoid inflammation, which causes an exacerbation of symptoms about four days after treatment begins if steroids are not used. By far the most commonly used medication is a combination of trimethoprim and sulfamethoxazole (co-trimoxazole, with the tradenames Bactrim, Septrin, or Septra), but some patients are unable to tolerate this treatment due to allergies. Other medications that are used, alone or in combination, include pentamidine, trimetrexate, dapsone, atovaquone, primaquine, and clindamycin. Treatment is usually for a period of about 21 days.

Nomenclature

The name P. jiroveci, to distinguish the organism found in humans from variants of Pneumocystis found in other animals, was first proposed in 1976, in honor of Otto Jirovec, who described Pneumocystis pneumonia in humans in 1952. After DNA analysis showed significant differences in the human variant, the proposal was made again in 1999 and has come into common use; P. carinii still describes the species found in rats. The International Code of Botanical Nomenclature would normally require the name to be spelled jirovecii rather than jiroveci; both spellings are currently in use.

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