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Pneumocystis Carinii Pneumonia

Pneumocystis Carinii Pneumonia

Alternate Names

  • PCP
  • Pneumonia


The organism Pneumocystis jiroveci (formerly called Pneumocystis carinii) causes pneumonia in people with weakened immune systems.

What is going on in the body?

By the time children turn 4 years old, 3 out of 4 will have acquired an organism called Pneumocystis jiroveci. This organism was formerly classified as a parasite but is now considered to be a fungus. It is very common in the environment.
Because most people are exposed to it and it causes no symptoms in a person with a normal immune system, there is no strategy for prevention of the infection per se. Rather, the occurrence of an illness (generally pneumonia) due to this fungus is a signal that something is likely to be wrong with a person's immune system.
Before the HIV epidemic was recognized in the early 1980s, Pneumocystis jiroveci pneumonia, or PJP (then called PCP for Pneumocystis carinii pneumonia), was most often seen in children who had congenital immune deficiencies, or in those whose immune systems were weakened by cancer or chemotherapy.
In fact, the recognition of PCP (now called PJP) in otherwise healthy homosexual men was the first clue to the HIV epidemic in the U.S.


What are the causes and risks of the infection?

Pneumocystis jiroveci causes PJP. People with weakened immune systems are at risk for serious illness.


What can be done to prevent the infection?

Giving preventive antibiotics, such as trimethoprim/sulfamethoxazole (i.e., Bactrim, Septra), dapsone, or pentamidine (i.e., Pentam), to those with weakened immune systems markedly cuts down the chances of getting the disease.


How is the infection diagnosed?

The organism can be seen in secretions from the lung or the lung tissue itself with the aid of a microscope. Special tests that check for antibodies and other substances can also be used to detect the organism.

Long Term Effects

What are the long-term effects of the infection?

Death is not uncommon when PJP is not treated in people with weakened immune systems, especially young children.

Other Risks

What are the risks to others?

There probably are no significant risks to others from a person with PJP, because most people are exposed to the organism constantly anyway.


What are the treatments for the infection?

Trimethoprim/sulfamethoxazole (i.e., Bactrim, Septra) is the antibiotic most commonly used to treat or prevent PJP. Corticosteroids such as prednisone are often used to help reduce inflammation and other symptoms of PJP. Other drugs used to treat PJP include dapsone plus trimethoprim (i.e., Primsol), pentamidine (i.e., Pentam), clindamycin (i.e., Cleocin) plus primaquine, trimetrexate (i.e., Neutrexin) plus leucovorin, or atovaquone (i.e., Mepron).

Side Effects

What are the side effects of the treatments?

The most common side effects of trimethoprim-sulfamethoxazole are upset stomach, rash, and increased sensitivity to natural or artificial sunlight.

After Treatment

What happens after treatment for the infection?

A person with an immune system weak enough to get PJP needs to continue taking preventive medication to keep PJP from recurring.

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