Overview, Causes, & Risk Factors

The organism Pneumocystis carinii causes pneumonia, especially 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 carinii. People are believed to get it from the environment or from contact with others who are infected, but this is not known for sure.

Usually infection during early childhood causes no symptoms. When a child or adult has a weakened immune system, though, it may cause severe pneumonia. Pneumocystis carinii pneumonia, or PCP, is the most common serious infection by a normal inhabitant of the body found in children infected with the AIDS virus. Adults and children whose immune systems have been weakened by chemotherapy, AIDS, or other conditions can become severely ill with PCP. This is also true of malnourished and premature babies.

What are the causes and risks of the infection?

Pneumocystis carinii causes PCP. People with weakened immune systems are at risk for serious illness.

Symptoms & Signs

What are the signs and symptoms of the infection?

Signs and symptoms of PCP include:

Diagnosis & Tests

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 be used to detect the organism, too.

Prevention & Expectations

What can be done to prevent the infection?

Giving preventive antibiotics, such as trimethoprim/sulfamethoxazole, dapsone, or pentamidine, to those with weakened immune systems markedly cuts down the chances of getting the disease.

What are the long-term effects of the infection?

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

What are the risks to others?

There probably are no risks to others, but no one is sure exactly how PCP is spread.

Treatment & Monitoring

What are the treatments for the infection?

Trimethoprim sulfamethoxazole is the antibiotic most commonly used to treat or prevent PCP. Corticosteroids such as prednisone are often used to help lessen inflammation and other symptoms of PCP.

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.

What happens after treatment for the infection?

Most people who have PCP have weak immune systems. Even after completing treatment, they need to continue taking preventive antibiotics to keep PCP from recurring.