What is pneumocystis pneumonia?

Definition

Pneumocystis pneumonia (PCP) is a lung infection caused by the fungus
Pneumocystis jiroveci (formerly called P.
carinii). This preventable infection affects people who have a weakened immune system, and it is
the most common serious infection among people with acquired immunodeficiency
syndrome (AIDS).

Causes

Most scientists believe that P. jiroveci is spread in the air.
It is not clear if it lives in soil or elsewhere. In healthy people, the fungus
can exist in the lungs without causing pneumonia. However, in people who have a
weakened immune system, PCP may cause a lung infection.

Risk Factors

People who are at increased risk for PCP include those who have AIDS or
cancer and those who are being treated for cancer.

Symptoms

Symptoms of PCP usually develop over the course of a few weeks or months. The main symptoms are shortness of breath, fever, dry cough, tightness in the chest, and weakness. One should consult a doctor immediately if experiencing any of these symptoms.

Screening and Diagnosis

A sample of the patient’s sputum is examined under a microscope. Sputum is
mucus from the lungs that is produced when one coughs. The doctor will collect
samples by giving the patient a vapor treatment to induce coughing or through a
bronchoscopy, an instrument that is inserted into the
airway.

Treatment and Therapy

Treatment will depend on the seriousness of the infection. For mild cases, the patient will be given medication in pill form. For severe cases, the patient will probably be treated in a hospital and receive medication by IV (intravenously).

Several drugs are used to treat PCP, including trimethoprim-sulfamethoxazole (TMP-SMZ, Bactrim, Septra,
Cotrim), which is available in pill and liquid forms; dapsone plus trimethoprim;
primaquine plus clindamycin; atovaquone; pentamidine (given by IV); trimetrexate
plus folinic acid; and corticosteroids, given in severe cases
when blood oxygen pressure falls below a certain level. Most of these treatments
have side effects. Even when treatment is given for PCP, the death rate is 15 to
20 percent.

Prevention and Outcomes

Persons who are at risk for PCP may be given medicine to prevent the disease.
In general, for those with human immunodeficiency virus (HIV)
infection, preventing PCP with medication is recommended if that person’s CD4 cell
count falls below 200. Other conditions, such as having a temperature higher than
100° Fahrenheit that lasts for more than two weeks or getting a fungal
infection in the mouth or throat, are reasons to start
preventive therapy. Some of the same drugs used to treat an infection can be taken
regularly to prevent the infection. These drugs include TMP-SMZ, dapsone,
atovaquone, and pentamidine aerosol.

If a person gets PCP once, he or she is more likely to get it again. Each time one gets it, the PCP causes damage to the lungs. The body can suffer side effects from the drugs.

Pneumonia vaccine only protects against a different kind of pneumonia. It will not keep a person from getting PCP.

Bibliography

AIDS InfoNet. “Pneumocystis Pneumonia (PCP).” Available at http://www.aidsinfonet.org.

American Academy of Family Physicians. “Pneumocystis Pneumonia (PCP) and HIV.” Available at http://familydoctor.org.

Centers for Disease Control and Prevention, National Center for HIV, STD, and TB Prevention. “You Can Prevent PCP: A Guide for People with HIV Infection.” Available at http://www.cdc.gov/hiv.

Corrin, Bryan, and Andrew G. Nicholson. Pathology of the Lungs. 2d ed. New York: Churchill Livingstone/Elsevier, 2006.

EBSCO Publishing. DynaMed: “Pneumocystis carinii”Pneumonia. Available through http://www.ebscohost. com/dynamed.

Fan, Hung Y., Ross F. Conner, and Luis P. Villarreal. AIDS: Science and Society. 5th ed. Sudbury, Mass.: Jones and Bartlett, 2007.

Hughes, Walter T. “Pneumocystis carinii” Pneumonitis. 2 vols. Rev. ed. Boca Raton, Fla.: CRC Press, 1987.

West, John B. Pulmonary Pathophysiology: The Essentials. 7th ed. Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins, 2008.