Pneumonias due to microorganisms that do not often cause disease in healthy people can occur in people who have a weakened immune system.
Symptoms vary but may include shortness of breath, cough, and fever.
X-rays of the chest are often combined with examinations of sputum and blood samples to make the diagnosis.
Antibiotics or antifungal or antiviral drugs are used to treat this pneumonia, and any immune system problem is treated.
Immunocompromised people have a weakened or impaired immune system. The immune system Immune Response Natural barriers and the immune system defend the body against organisms that can cause infection. (See also Lines of Defense.) Natural barriers include the skin, mucous membranes, tears, earwax... read more defends the body against microorganisms that can cause infection.
In people with a weakened immune system, pneumonia may be caused by many microorganisms, including those that do not usually cause pneumonia. Many conditions may cause weakness of the immune system, including
(See also Overview of Pneumonia Overview of Pneumonia Pneumonia is an infection of the small air sacs of the lungs (alveoli) and the tissues around them. Pneumonia is one of the most common causes of death worldwide. Often, pneumonia is the final... read more .)
In people with a weakened immune system, pneumonia may be caused by the same microorganisms that cause community-acquired pneumonia Causes Community-acquired pneumonia is lung infection that develops in people outside a hospital. Many bacteria, viruses, and fungi can cause pneumonia. The most common symptom of pneumonia is a cough... read more but can be caused by unusual or uncommon organisms.
Pneumocystis jirovecii is a common fungus that may reside harmlessly in the lungs of healthy people. It usually causes pneumonia only when the body’s defenses are weakened Overview of Pneumonia Pneumonia is an infection of the small air sacs of the lungs (alveoli) and the tissues around them. Pneumonia is one of the most common causes of death worldwide. Often, pneumonia is the final... read more because of AIDS, organ transplantation, cancer, or use of drugs that alter the immune system. Often, P. jirovecii pneumonia is the first indication that a person with human immunodeficiency virus Human Immunodeficiency Virus (HIV) Infection Human immunodeficiency virus (HIV) infection is a viral infection that progressively destroys certain white blood cells and can cause acquired immunodeficiency syndrome (AIDS). HIV is transmitted... read more (HIV) infection has developed AIDS.
Other fungi such as Aspergillus Aspergillosis Aspergillosis is an infection, usually of the lungs, caused by the fungus Aspergillus. A ball of fungus fibers, blood clots, and white blood cells may form in the lungs or sinuses. People may... read more and Candida Candidiasis Candidiasis is a fungal infection caused by several species of the yeast Candida, especially Candida albicans. The most common type of candidiasis is a superficial infection of the mouth, vagina... read more , bacteria such as Staphylococcus aureus Staphylococcus aureus Infections Staphylococcus aureus is the most dangerous of all of the many common staphylococcal bacteria. These gram-positive, sphere-shaped (coccal) bacteria (see figure How Bacteria Shape Up) often cause... read more , Streptococcus pneumoniae Streptococcal Infections Streptococcal infections are caused by any one of several species of Streptococcus. These gram-positive, sphere-shaped (coccal) bacteria (see figure How Bacteria Shape Up) cause many disorders... read more , and Haemophilus influenzae Haemophilus influenzae Infections Haemophilus influenzae are gram-negative bacteria that can cause infection in the respiratory tract, which can spread to other organs. Infection is spread through sneezing, coughing, or touching... read more , and viruses such as cytomegalovirus Cytomegalovirus (CMV) Infection Cytomegalovirus infection is a common herpesvirus infection with a wide range of symptoms: from no symptoms to fever and fatigue (resembling infectious mononucleosis) to severe symptoms involving... read more and herpes simplex virus Herpes Simplex Virus (HSV) Infections Herpes simplex virus infection causes recurring episodes of small, painful, fluid-filled blisters on the skin, mouth, lips (cold sores), eyes, or genitals. This very contagious viral infection... read more also cause pneumonia in people with a weakened immune system.
Symptoms of pneumonia in people who have a weakened immune system may be the same as those for community-acquired pneumonia Symptoms Community-acquired pneumonia is lung infection that develops in people outside a hospital. Many bacteria, viruses, and fungi can cause pneumonia. The most common symptom of pneumonia is a cough... read more and include the following:
These symptoms can develop rapidly or slowly.
Most people who have P. jirovecii pneumonia develop a fever, shortness of breath, and a dry cough, often slowly. The lungs may not be able to deliver sufficient oxygen to the blood, leading to shortness of breath that is sometimes severe.
The diagnosis of pneumonia in a person who has a weakened immune system is based on the person’s symptoms, the results of a chest x-ray or CT scan, and the results of sputum and blood tests.
Chest x-rays may be normal or may show signs of infection.
Doctors obtain sputum samples by giving a vapor treatment that causes the person to cough deeply (inducing sputum production) or insert a bronchoscope Bronchoscopy Bronchoscopy is a direct visual examination of the voice box (larynx) and airways through a viewing tube (a bronchoscope). A bronchoscope has a camera at the end that allows a doctor to look... read more (small flexible tube equipped with a camera) into the airways. Sputum samples obtained by inducing a cough and particularly those obtained with a bronchoscope are less likely to contain saliva and are more likely than expectorated sputum samples to allow doctors to identify the organism causing pneumonia.
Doctors usually take a sample of blood so they can try to grow (culture) the bacteria in the laboratory and identify it.
People who have a weakened immune system may have low levels of oxygen in their blood. Doctors can measure levels of oxygen in the blood without taking a blood sample by placing a sensor on a finger or an earlobe. This test is called pulse oximetry Pulse oximetry Both arterial blood gas testing and pulse oximetry measure the amount of oxygen in the blood, which helps determine how well the lungs are functioning. Arterial blood gas tests are invasive... read more .
Even when the pneumonia is treated, the overall death rate is higher than that for generally healthy people with community-acquired pneumonia Community-Acquired Pneumonia Community-acquired pneumonia is lung infection that develops in people outside a hospital. Many bacteria, viruses, and fungi can cause pneumonia. The most common symptom of pneumonia is a cough... read more because infections are much harder to treat in people with immune system problems and because these people tend to be much sicker, even before pneumonia begins.
The overall death rate for people who have P. jirovecii pneumonia is high.
Doctors often give treatments to help bolster the person's immune system and prevent pneumonia. For example, in people whose immune system has been weakened by cancer treatment, doctors may give a drug called granulocyte-colony stimulating factor to enhance the production of white blood cells (the type that fight infection).
People who are at risk of pneumonia caused by bacteria should receive vaccinations against pneumococcus Pneumococcal Vaccine Pneumococcal vaccines help protect against bacterial infections caused by Streptococcus pneumoniae (pneumococci). Pneumococcal infections include ear infections, sinusitis, pneumonia, bloodstream... read more and Haemophilus influenzae Haemophilus influenzae Type b Vaccine The Haemophilus influenzae type b (Hib) vaccine helps protect against bacterial infections due to Hib, such as pneumonia and meningitis. These infections may be serious in children. Use of the... read more .
The combination antibiotic trimethoprim/sulfamethoxazole can be used to help prevent P. jirovecii pneumonia in people at risk. This drug’s side effects, which are particularly common among people who have AIDS, include rashes, a reduced number of infection-fighting white blood cells, and fever. Alternative preventive drug treatments are dapsone or pentamidine.
Treatment of pneumonia depends on the
Doctors usually give an antibiotic that is effective against many organisms (a broad-spectrum antibiotic). If the person's condition does not improve, doctors may add an additional drug that is effective against viruses or fungi.
Therapies to improve the immune system Treatment Immunodeficiency disorders involve malfunction of the immune system, resulting in infections that develop and recur more frequently, are more severe, and last longer than usual. Immunodeficiency... read more are also important for the treatment of pneumonia in people with immune system problems. Drugs that suppress the immune system (such as chemotherapy drugs or drugs used to treat autoimmune disorders) should be temporarily stopped until the infection has resolved.
People who have P. jirovecii pneumonia are given the combination antibiotic trimethoprim/sulfamethoxazole Alternative drugs are dapsone, atovaquone, clindamycin, and pentamidine. Some people are also given the corticosteroid prednisone.