Pneumocystis pneumonia
| Pneumocystis jirovecii pneumonia | |
|---|---|
 |
|
| Pneumocystis jirovecii cysts from bronchoalveolar lavage, stained with Toluidine blue O stain | |
| Classification and external resources | |
| Specialty | Pulmonology |
| ICD-10 | ICD9 = 136.3 |
| DiseasesDB | 10160 |
| MedlinePlus | 000671 |
| eMedicine | med/1850 |
| MeSH | D011020 |
Pneumocystis pneumonia (PCP) is a form of pneumonia, caused by the yeast-like fungus Pneumocystis jirovecii.
Pneumocystis pneumonia is not commonly found in the lungs of healthy people, but, being a source of opportunistic infection, it can cause a lung infection in people with a weak immune system. Pneumocystis pneumonia is especially seen in people with cancer undergoing chemotherapy, HIV/AIDS, and the use of medications that suppress the immune system.
Signs and symptoms 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 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.
Pneumothorax is a well-known complication of PCP. An acute history of chest pain with breathlessness and diminished breath sounds is typical of pneumothorax.
The risk of PCP increases when CD4 positive T-cell levels are less than 200 cells/μL. In these immunosuppressed individuals the manifestations of the infection are highly variable. The disease attacks the interstitial, fibrous tissue of the lungs, with marked thickening of the alveolar septa and alveoli, leading to significant hypoxia which can be fatal if not treated aggressively. In this situation LDH levels increase and gas exchange is compromised. Oxygen is less 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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