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Pneumonia in People With a Weakened Immune System


Sanjay Sethi

, MD, University at Buffalo, Jacobs School of Medicine and Biomedical Sciences

Reviewed/Revised Feb 2024

Pneumonia is infection of the lungs. Pneumonia in people whose immune system is weakened or impaired (for example, by human immunodeficiency virus [HIV], cancer, organ transplantation, or the use of certain medications) is often caused by different organisms than those that cause pneumonia in healthy people.

  • 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.

  • Antibiotic, antifungal, or antiviral medications are used to treat this pneumonia, and any immune system problem is treated.

People who have a weakened or impaired immune system are described as being immunocompromised. The immune system Immune Response If the body did not have defenses against infection, it would quickly be overwhelmed by microorganisms. These defenses require a living, properly functioning body. A dead body begins to decay... 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

Causes of Pneumonia in People With a Weakened Immune System

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. The most common symptom of... read more Overview of Pneumonia because of 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 is treated with antiretroviral medications. If untreated, it can cause... read more Human Immunodeficiency Virus (HIV) Infection (HIV) infection, organ transplantation, cancer, or use of medications that alter the immune system. Often, P. jirovecii pneumonia is the first indication that a person with 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... 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... read more Candidiasis , 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 ) often cause skin infections... read more <i >Staphylococcus aureus</i> Infections , 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 ) cause many disorders, including... 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,... 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 Herpes Simplex Virus (HSV) Infections also cause pneumonia in people with a weakened immune system.

Symptoms of Pneumonia in People With a Weakened Immune System

  • A general feeling of weakness (malaise)

  • Cough that produces sputum (thick or discolored mucus)

  • Shortness of breath

  • Fever

  • Chills

  • Chest pain

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.

Diagnosis of Pneumonia in People With a Weakened Immune System

  • Chest x-ray

  • Microscopic examination of a sputum (thick or discolored mucus) sample

  • Blood cultures

  • Pulse oximetry

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 computed tomography (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, a thin viewing tube with a light, has a camera at the... read more Bronchoscopy (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 .

Treatment of Pneumonia in People With a Weakened Immune System

  • Antibiotics, antivirals, or antifungals

  • Treatment of any immune system problem

Treatment of pneumonia depends on the

  • Specific immune system problem

  • Severity of illness

  • Organisms that may be causing infection

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 medication 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. Medications that suppress the immune system (such as chemotherapy drugs or medications 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 medications are dapsone, atovaquone, clindamycin, and pentamidine. Some people with severe pneumonia due to P. jirovecii are also given the corticosteroid prednisone to reduce inflammation.

Prognosis for Pneumonia in People With a Weakened Immune System

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 who are not patients in a hospital, usually in people with a normal (competent) immune system, or in those who are immunocompromised... 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.

Prevention of Pneumonia in People With a Weakened Immune System

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 medication called granulocyte-colony stimulating factor to enhance the production of white blood cells (the type that fight infection).

The combination antibiotic trimethoprim/sulfamethoxazole can be used to help prevent P. jirovecii pneumonia in people at risk. The side effects of this medication include rashes, a reduced number of infection-fighting white blood cells, and fever. Side effects are particularly common among people who have AIDS. Alternative preventive medications are dapsone or pentamidine.

Drugs Mentioned In This Article

Generic Name Select Brand Names
Cleocin, Cleocin Ovules, Cleocin Pediatric, Cleocin T, CLIN, Clindacin ETZ, Clindacin-P, Clinda-Derm , Clindagel, ClindaMax, ClindaReach, Clindesse, Clindets, Evoclin, PledgaClin, XACIATO
NebuPent, Pentam
Deltasone, Predone, RAYOS, Sterapred, Sterapred DS
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