Pneumocystis jiroveci pneumonia (formerly called Pneumocystis carinii or PCP) is the most common opportunistic infection that occurs in AIDS patients. Originally, researchers thought a one-cell organism (protozoan) called Pneumocystis carinii caused the disease, but recent research suggests that a fungus called Pneumocystis jiroveci causes the pneumonia. However, the condition is still commonly referred to as PCP.
According to the U.S. Centers for Disease Control and Prevention (CDC), PCP is considered an AIDS-defining illness. This means that when HIV-infected patients develop PCP, their condition has progressed to AIDS.
Even if healthy individuals are exposed to Pneumocystis jiroveci, they do not typically develop PCP because they are able to inhibit the growth of the fungus. However, children and people with weakened immune systems, such as HIV/AIDS patients, are unable to adequately fight against the fungus.
Individuals with a CD4 cell (helper T-cells that help fight against disease and infection) count lower than 200 cells per microliter of blood have the greatest risk of developing PCP. Once the CD4 cell count falls below 200, the patient's condition has progressed to AIDS. Healthy individuals have a CD4 cell count between 600 and 1,200 per microliter of blood. In addition, people who have CD4 cell counts lower than 300 and have already had another opportunistic infection have an increased risk of developing PCP.
PCP almost always affects the lungs, causing a type of pneumonia. The first signs of PCP are difficulty breathing, fever, and a dry cough.
Mortality used to range from 20-40%, depending on the severity of the disease. Mortality rates have decreased to about 10-20%. This is because PCP is almost entirely preventable with new drugs, and it can be treated effectively with medication. Without HIV treatment, more than 85% of HIV/AIDS-infected patients would develop PCP.
Unfortunately, PCP is still common in people who are infected with HIV for a long time before getting treatment. In fact, 30-40% of AIDS patients develop PCP if they wait to get treatment until their CD4 cell counts are around 50 cells per microliter of blood.
Patients who are not infected with HIV have a higher mortality rate, which ranges from 30-50%, according to medical literature. The higher incidence of mortality is likely a result of a delay in diagnosis and initiation of appropriate treatment.
According to the CDC, healthcare providers should discuss preventative treatment with patients who have CD4 cell counts lower than 300.
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