Healthy Living

What Is Pneumocystis Carinii Pneumonia?

What Is Pneumocystis Carinii Pneumonia?

Pneumocystis carinii pneumonia (PCP) is a very serious disease, which is characterized by a fluid buildup and inflammation in the lungs. This lung infection is caused by the fungus Pneumocystis jiroveci. It is an opportunistic disease that usually infects immunosuppressed individuals, especially those with HIV. Pneumocystis carinii pneumonia (PCP) has the likelihood of spreading through the air, increasing its exposure to children around the ages of 3 or 4. Although it’s a rare infection, it can also affect other parts of your body such as the liver, lymph nodes, and the bone marrow.

PCP was a very rare infection until the epidemic of the acquired immunodeficiency syndrome (AIDS) in the early 1980s. Before this epidemic, the infection was common to people with acute lymphocytic leukemia (ALL), protein malnutrition, and those under corticosteroid therapies.

What are the risk factors of PCP?

PCP is caused by a fungus formally known as Pneumocystis carinii. This fungus is currently known as Pneumocystis jiroveci. It is very hard to get this infection under normal immune conditions. Below are the risk factors leading to PCP:

  • history of lung disease
  • organ transplant patients
  • patients taking immunosuppressants and steroids
  • people with hematologic malignancies (blood and lymph system cancer)
  • people with HIV experiencing fever and oral thrush
  • extreme malnutrition
  • congenital immune deficiency
  • connective tissue diseases e.g. rheumatoid arthritis

Signs and Symptoms of PCP

The most important thing that you should know about PCP is that it does show its symptoms during the early stages. However, if you are HIV-positive or have a weakened immune system and you experience the following symptoms, having PCP can be dangerous. The symptoms are:

PCP can also be graded according to its severity. PCP develops under three major stages:

Mild PCP

Mild PCP is the earliest stage of a PCP infection. It is characterized by:

  • minor or normal lung infiltrates
  • shortness of breath during mild exercises (accompanied by sweats and cough)
  • a decreased oxygen saturation even at rest
  • arterial blood gas (ABG) analysis that shows hypoxia (decreased oxygen in the body)

Moderate PCP

This stage is characterized by:

  • breathlessness even on minimal exercises
  • fever with or without sweats
  • diffuse interstitial shadowing (thickening of tissues around the small airways and airspaces)

Severe PCP

It is the most critical stage of PCP. It is characterized by:

  • shortness of breath even at rest
  • a persistent cough and fever
  • thickened tissues around the small airways in the lungs
  • a decreased saturation of oxygen at rest

Diagnosis of Pneumocystis carinii Pneumonia (PCP)

During the diagnosis of PCP, your doctor will examine you carefully and ask you some questions regarding your signs and symptoms. After that, your health care provider can opt for any of the following tests:

Blood Tests

The following tests are monitored:

  • Lactate Dehydrogenase -any increase in LDH indicates that you have PCP. This test is not highly sensitive.
  • A-a Gradient or Alveolar-Arterial Oxygen Tension - an increase in test is indicative of a PCP diagnosis.
  • Polymerase Chain Reaction (PCR) test - is a test that is recommended during the early stages of a PCP infection. It is mostly done for people who are HIV-positive.
  • Serum (1-3)-beta-d-glucan - an increased level of (1-3)-beta-d-glucan is an indication of a PCP infection.
  • Arterial Blood Gas - an ABG may either show hypocarbia or hypoxia due to lung hyperventilation.


Microbiology can also be used as a diagnostic test for PCP. The following tests are applied in the diagnosis of PCP:

  • Open lung biopsy - can be employed occasionally for the diagnosis of PCP.
  • Sputum extract - sputum is cultured and the detected by staining the cyst. Silver-based stains are mostly used for this test. Repeated samples may be cultured to confirm the diagnosis of PCP. Sputum may also be collected after inhalation of nebulized saline. This sputum is then sent for mycobacterial culture for diagnosis.
  • Bronchoscopy or Biopsy - if the sputum is negative but PCP is still suspected by your health care provider, then it undergoes further test known as bronchoscopy or biopsy to identify the organism.


Radiology is also another important diagnostic test for PCP. In radiology the following is done:

  • Chest X-ray test - PCP is diagnosed if this test shows pneumothorax of perihilar shadows.
  • Standard CT - this test is recommended but it has low specificity and sensitivity.
  • High-resolution CT scanning - this type of CT imaging has 100% sensitivity and 89% specificity.
  • Gallium Scanning - this type of scan has high sensitivity but has a low and variable specificity.

Pulmonary Function Test

A pulmonary function test can also be important in a PCP diagnosis. It shows the following:

  • It can show a latent reduction in the lung vital capacity and the total lung capacity of the patient.
  • It shows a decrease in a single breath diffusion capacity for carbon monoxide (DLCO). This test has a sensitivity of 89 percent.

Can PCP Be Prevented?

Yes, PCP is an infection that can be prevented through different therapeutic measures. Below is a list of conditions, which preventive therapy for PCP is recommended:

  • organ transplant patients
  • HIV-positive patients with CD4 counts below 200 cells/microliter
  • patients who underwent a bone marrow transplant
  • patients who have taken corticosteroids for a long time and at a high dosage
  • people who have a history of PCP
  • people who have taken immunosuppressive drugs for a long time

If you have the aforementioned conditions, then a vaccine is available for you. This type of vaccine is aimed to raise your CD4 count, hence, preventing PCP. If you are a smoker, you should quit smoking to make this type of vaccine effective.

Another important step you can take to prevent PCP is starting the treatment drugs before your CD4 cell count drops. You can take the same drugs used to treat PCP for prevention purposes but at different doses as prescribed by your doctor.

How Is PCP treated?

If you have PCP, your doctor will likely to recommend the antibiotics Septra, Bactrim, or Cotrim. These drugs are made from a combination of two antibiotics namely sulfamethoxazole and trimethoprim. Depending on the severity of your condition, SMZ-TMP can be administered orally as a pill or through intravenous injections. SMZ-TMP is mainly combined with some oral steroids.

Some people may be allergic to SMZ since it is a sulfa drug. In such a case, your doctor may recommend another medication. Other drugs that can be used to treat PCP include:

  • Mepron - is also known as atovaquone and is taken as a liquid. It is used when you can’t take pentamidine or SMZ-TMP.
  • Dapsoneis a drug that is taken in the form of pills. It is sometimes combined with pyrimethamine or TMP.
  • Pentamidine - is a drug that is inhaled as an aerosol through a nebulizer. You can do the inhalation procedure at your doctor’s office. This drug is also administered though intravenous injections in severe cases of PCP.

The Bottom Line

Pneumocystis carinii pneumonia (PCP) is a very serious opportunistic infection, which is characterized by a fluid buildup and inflammation in the lungs. This disease usually affects people who have weak immune systems such as people with HIV. It is a disease that can be prevented and treated as well. Better management of this condition through prevention and cure can reduce its effects.