The Facts About Pneumocystis Pneumonia (PCP)

Opportunistic Infection Still Associated with High Risk of Illness and Death

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What Is PCP?

Pneumocystis jiroveci pneumonia (PCP) is a potentially deadly opportunistic infection commonly seen in people with HIV. It is caused by a fungus (P. jiroveci) which typically only manifests with pneumonia in persons with severely compromised immune systems.

Previously known as Pneumocystis carinii pneumonia, the disease was widely seen in the early part of the AIDS epidemic. Today, with improved and earlier antiretroviral treatment (ART), the incidence of PCP has dropped dramatically although it still remains a leading cause of illness and death among people with HIV worldwide.

How Do I Know If I Have PCP?

PCP is most typically associated with immune suppression, meaning that your immune system is unable to defend against infections that other people. The first signs of PCP are not unlike that of other pneumonia, presenting with fever, cough, shortness of breath, weight loss and night sweats. Coughs are generally non-productive, meaning that there will not be any significant discharge (mostly due to the thick, viscous nature of the sputum in the lungs).

How Do You Get PCP?

P. jiroveci is prevalent worldwide with as many as 75% of children testing positive by age 4. The specific mode of primary transmitted is still unknown, but there are some who believe the fungus can be spread from person to person. As such, while avoidance of the P. jiroveci itself is difficult, it's important to remember that the fungus can only cause disease if your immune system is weak and unable to fight it.

How Is PCP Diagnosed?

The initial diagnosis can generally be made from a check x-ray, which will show diffuse infiltrates throughout the lung (as opposed to concentrates in specific portions of the lung). A test used to measure the arterial oxygen levels will be strikingly low compared to what one might expect from the outward symptoms.

Microscopic examination of lung fluid or tissue provide definitive confirmation of infection (see image). A polymerase chain reaction (PCR) assay may also be used to detect P. jiroveci DNA.

Can I Protect Myself from PCP?

The risk of PCP in persons with compromised immune systems can be significantly reduced with the use of a prophylactic (preventive) drug called TMP-SMX (trimethoprim/sulfamethoxazole). Commonly known as co-trimoxazole or Bactrim, the drug is often prescribed once a pefson's CD4 count drops below 200.

In the event of an allergy to TMP-SMX, other drugs can be prescribed including dapsone and pentamidine (although the latter is being used far less frequently due to high levels of side effects).

Ultimately, the best way to avoid PCP is to prevent the depletion of your immune response. This can best be accomplished by the early testing and treatment of HIV. By initiating therapy at the time diagnosis, you can prevent the deterioration of your immune function and, with it, the risk of PCP.

What Are the Side Effects of TMP-SMX?

TMP-SMS can cause rash, nausea, fever and headache in some people. Most of these symptoms are transient and mild, resolving a few days to a week. Unless a drug reaction is severe, treatment should not be stopped in persons with a high risk for PCP.

Topical or oral medications can often be prescribed to treat the symptoms. Dapsone can be substituted if TMP-SMX is intolerable.

I Was Vaccinated for Pneumonia. Won’t That Protect Me Against PCP?

No. What you were given was the Pneumovax vaccine, which protects you from bacterial pneumonia, not PCP. There is currently no vaccine for PCP.


Centers for Disease Control and Prevention (CDC). "Pneumocystis Pneumonia | Fungal Diseases."

Ponce, C.; Gallo, M.; Bustamante, R. et al. "Pneumocystis colonization is highly prevalent in the autopsied lungs of the general population." Clinical Infectious Diseases. 2010; 50(3): 347-353.

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