Pneumocystis jirovecii pneumonia pathophysiology: Difference between revisions
| Line 1: | Line 1: | ||
{{Pneumocystis jirovecii pneumonia}}{{CMG}} | {{Pneumocystis jirovecii pneumonia}}{{CMG}} | ||
==Overview== | ==Overview== | ||
==Pathophysiology== | |||
[[Image:Pneumocystis LifeCycle.gif|left|thumb|300px|Life cycle of Pneumocystis spp.]] | [[Image:Pneumocystis LifeCycle.gif|left|thumb|300px|Life cycle of Pneumocystis spp.]] | ||
Pneumocystis jirovecii (previously classified as Pneumocystis carinii) was previously classified as a protozoa. Currently, it is considered a fungus based on nucleic acid and biochemical analysis. | Pneumocystis jirovecii (previously classified as Pneumocystis carinii) was previously classified as a protozoa. Currently, it is considered a fungus based on nucleic acid and biochemical analysis. | ||
===Life Cycle=== | |||
The complete life-cycles of any of the species of ''Pneumocystis'' are not known, but presumably all resemble the others in the genus. The terminology follows zoological terms, rather than mycological terms, reflecting the initial misdetermination as a protozoan parasite. All stages are found in lungs and because they cannot be cultured, direct observation of living ''Pneumocystis'' is difficult. The trophozoite stage is the vegetative state. It is single-celled and appears amoeboid (multilobed) and closely associated with host cells. Globular cysts eventually form that have a thicker wall. Within these [[ascus]]-like cysts, eight spores form which are released through rupture of the cyst wall. The cysts often collapse forming crescent-shaped bodies visible in stained tissue. It is not known for certain if [[meiosis]] takes place within the cysts, or what the genetic status is of the various cell types [http://www.dpd.cdc.gov/dpdx/HTML/Pneumocystis.htm - see DPDx life-cycle diagram]. | |||
This is a generalized life cycle proposed by John J. Ruffolo, Ph.D. (Cushion, MT, 1988) for the various species of Pneumocystis. These fungi are found in the lungs of mammals where they reside without causing overt infection until the host's immune system becomes debilitated. Then, an oftentimes lethal pneumonia can result. '''1''' Asexual phase: trophic forms replicate by mitosis '''2''' to '''3'''. Sexual phase: haploid trophic forms conjugate '''1''' and produce a zygote or sporocyte (early cyst) '''2'''. The zygote undergoes meiosis and subsequent mitosis to produce eight haploid nuclei (late phase cyst) '''3'''. Spores exhibit different shapes (such as, spherical and elongated forms). It is postulated that elongation of the spores precedes release from the spore case. It is believed that the release occurs through a rent in the cell wall. After release, the empty spore case usually collapses, but retains some residual cytoplasm '''4'''. A trophic stage, where the organisms probably multiply by binary fission is also recognized to exist. The organism causes disease in immunosuppressed individuals. | This is a generalized life cycle proposed by John J. Ruffolo, Ph.D. (Cushion, MT, 1988) for the various species of Pneumocystis. These fungi are found in the lungs of mammals where they reside without causing overt infection until the host's immune system becomes debilitated. Then, an oftentimes lethal pneumonia can result. '''1''' Asexual phase: trophic forms replicate by mitosis '''2''' to '''3'''. Sexual phase: haploid trophic forms conjugate '''1''' and produce a zygote or sporocyte (early cyst) '''2'''. The zygote undergoes meiosis and subsequent mitosis to produce eight haploid nuclei (late phase cyst) '''3'''. Spores exhibit different shapes (such as, spherical and elongated forms). It is postulated that elongation of the spores precedes release from the spore case. It is believed that the release occurs through a rent in the cell wall. After release, the empty spore case usually collapses, but retains some residual cytoplasm '''4'''. A trophic stage, where the organisms probably multiply by binary fission is also recognized to exist. The organism causes disease in immunosuppressed individuals. | ||
Revision as of 15:58, 27 September 2012
|
Pneumocystis jirovecii pneumonia Microchapters |
|
Differentiating Pneumocystis jirovecii pneumonia from other Diseases |
|
Diagnosis |
|
Treatment |
|
Case Studies |
|
Pneumocystis jirovecii pneumonia pathophysiology On the Web |
|
American Roentgen Ray Society Images of Pneumocystis jirovecii pneumonia pathophysiology |
|
Pneumocystis jirovecii pneumonia pathophysiology in the news |
|
Risk calculators and risk factors for Pneumocystis jirovecii pneumonia pathophysiology |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Pathophysiology
Pneumocystis jirovecii (previously classified as Pneumocystis carinii) was previously classified as a protozoa. Currently, it is considered a fungus based on nucleic acid and biochemical analysis.
Life Cycle
The complete life-cycles of any of the species of Pneumocystis are not known, but presumably all resemble the others in the genus. The terminology follows zoological terms, rather than mycological terms, reflecting the initial misdetermination as a protozoan parasite. All stages are found in lungs and because they cannot be cultured, direct observation of living Pneumocystis is difficult. The trophozoite stage is the vegetative state. It is single-celled and appears amoeboid (multilobed) and closely associated with host cells. Globular cysts eventually form that have a thicker wall. Within these ascus-like cysts, eight spores form which are released through rupture of the cyst wall. The cysts often collapse forming crescent-shaped bodies visible in stained tissue. It is not known for certain if meiosis takes place within the cysts, or what the genetic status is of the various cell types - see DPDx life-cycle diagram.
This is a generalized life cycle proposed by John J. Ruffolo, Ph.D. (Cushion, MT, 1988) for the various species of Pneumocystis. These fungi are found in the lungs of mammals where they reside without causing overt infection until the host's immune system becomes debilitated. Then, an oftentimes lethal pneumonia can result. 1 Asexual phase: trophic forms replicate by mitosis 2 to 3. Sexual phase: haploid trophic forms conjugate 1 and produce a zygote or sporocyte (early cyst) 2. The zygote undergoes meiosis and subsequent mitosis to produce eight haploid nuclei (late phase cyst) 3. Spores exhibit different shapes (such as, spherical and elongated forms). It is postulated that elongation of the spores precedes release from the spore case. It is believed that the release occurs through a rent in the cell wall. After release, the empty spore case usually collapses, but retains some residual cytoplasm 4. A trophic stage, where the organisms probably multiply by binary fission is also recognized to exist. The organism causes disease in immunosuppressed individuals.