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'''''Pneumocystis jiroveci''''' cysts from bronchoalveolar lavage, stained with Toluidin Blue O Stain
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or '''''Pneumocystis'' pneumonia''' ('''PCP''') is a form of
Pneumonia caused by the yeast-like
Fungal Microorganism ''
Pneumocystis Jiroveci '' (sometimes spelled ''jirovecii'' and formerly classified as ''Pneumocystis carinii''). ''Jiroveci'' is pronounced 'yee row vet zee.'
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 .
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.
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 (pO
2) 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
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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.
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.
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.
1 The
International Code Of Botanical Nomenclature would normally require the name to be spelled ''jirovecii'' rather than ''jiroveci''; both spellings are currently in use.
The term PCP, which was widely used by practitioners and patients, has been retained for convenience, with the rationale that it now stands for the more general neumo'''c'''ystis '''p'''neumonia rather than neumocystis '''c'''arinii '''p'''neumonia.
The earliest report of this organism appears to have been that of
Carlos Chagas in 1909 who called it 'Schizotrypanum' and considered it to be a form of
Trypanosome infecting humans.
2 The discovery of this organism was confirmed by
Antonio Carini in 1910 also in
Brazil .
3 It was again reported in 1912 by Delanoë and Delanoë this time at the
Pasteur Institute in
Paris ,
France who found it in rats and who proposed the name ''Pneumocystis carinii'' after Carini.
4
It was redescribed as a human pathogen in 1942 by two Dutch investigators, van der Meer and Brug who found ''P. carinii'' in three new cases: a 3-month-old infant with congenital heart disease and in 2 of 104 autopsy cases - a 4-month-old infant and a 21-year-old adult.
5 Nine years later (1951) Dr. Josef Vanek at
Karls-Universität in
Praha ,
Czechoslovakia showed in a study of lung sections from sixteen children that ''P. carinii'' was the causative agent of pneumonia in these children.
6 The following year (1952) Jírovec reported ''P. carinii'' as the cause of interstitial pneumonia in neonates.
7,
8,9
