- Pneumocystis carinii is a microscopic fungus that affects the lungs, and is the most important cause of pneumonia in people with HIV/Aids.
- Common symptoms of PCP include tiredness, fever, breathlessness and a dry cough.
- Where tests to identify Pneumocystis are unavailable, a person will often be treated for PCP based on their symptoms alone.
- Treatment for PCP is usually with the medication co-trimoxazole.
- Anyone with a CD4 cell count below 200/ul is at risk for PCP, and should take daily co-trimoxazole to help prevent it.
What is pneumocystis carinii pneumonia (PCP)?
Pneumocystis carinii is a microscopic fungus that affects the lungs, and is the most important cause of pneumonia in people with HIV/AIDS. People with HIV usually become susceptible to pneumocystis carinii pneumonia (PCP) when their CD4 cell count falls below 200/ul. In many people, this will be the first illness that marks the onset of AIDS and around 80% of people with AIDS will get PCP at some time.
The risk of transmitting PCP from one person to another appears to be very small.
Symptoms and signs of PCP
The most common symptoms of PCP are tiredness, fever, breathlessness and a dry cough that does not produce sputum. Symptoms may begin quite suddenly or may develop over a few weeks. In hospital, an X-ray may show a typical pattern of widespread fluffiness in the lungs, and oxygen levels in the blood will be low because the lungs are not functioning properly.
Sometimes there are no symptoms, and physical examination, including examination of the lungs, may show few if any abnormalities.
How is PCP diagnosed?
If pneumonia is suspected, your doctor will order tests to help determine its severity. A chest X-ray may show a typical pattern of widespread fluffy patches in the lungs, known as "diffuse infiltrates". Tests to measure oxygen levels in the blood will be low because the lungs are not functioning properly. The oxygen level is first checked with an oximeter, a device that is placed on your fingertip. If the result of this test is abnormal, you may also need a test of arterial blood gases (ABG), in which a sample of blood is drawn from a wrist or thigh artery and sent to the laboratory for analysis. If your oxygen level is very low, you may require hospitalisation.
Many conditions that affect the lungs, including asthma, bronchitis, other types of pneumonia, and tuberculosis, may produce symptoms similar to PCP. To make sure the problem is PCP, your doctor will ask you to cough up fluid (sputum), which will be examined in the laboratory. Your doctor may arrange for you to have an induced sputum test. For this test, you are asked to inhale a salt water vapour to stimulate vigorous coughing that produces sputum from deep in the lungs. If induced sputum does not reveal Pneumocystis carinii, it may be necessary to perform bronchoscopy with lavage, in which a tube is inserted into the lungs to obtain a sputum sample.
However, it can be difficult to get a sputum sample from a person with PCP, and the tests to identify the fungus may not be available in all hospitals. Since PCP is a serious condition, a person with Aids will often be treated for PCP based on their symptoms alone i.e. without a definitive diagnosis.
If you do have access to the above tests (chest x-ray, oximetry and induced sputum test), but these turn out to be negative and your symptoms are mild, your doctor may suggest trying medications for asthma or bronchitis to see if this improves your condition, or performing additional lung tests.
How is PCP treated?
Treatment for PCP is usually co-trimoxazole (“Bactim”, “Septran”, “Purbac”), which is given intravenously in severe cases or orally in mild cases. In severe cases, prednisone may be added to reduce inflammation in the lungs. Treatment is for 14 – 21 days. Patients with very low oxygen levels will need supplementary oxygen by a face mask or even via a ventilator.
Anyone with a CD4 cell count below 200/ul should take daily co-trimoxazole to prevent PCP. Anyone who has had a first episode of PCP must take daily co-trimoxazole for the rest of their lives to prevent recurrences.
Even with treatment, about one in five people will die of PCP.
What can I do to prevent PCP?
Anyone with a CD4 cell count below 200/ul is at risk for PCP, and should take daily co-trimoxazole to help prevent it.
Prophylaxis (preventive treatment) can be discontinued if the CD4 count rises above 200/ul for three months on antiretroviral therapy.