HIV coinfection with tuberculosis pathophysiology
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Differentiating HIV coinfection with tuberculosis from other Diseases |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
The likelihood of getting sick with other infections and diseases is much more in HIV-infected individuals. Tuberculosis (TB) is one of these diseases. TB commonly affects the lungs; however, It can sometimes affects other organs and body parts, such as the brain, heart, kidneys, or spine.
Pathophysiology
- HIV infection weakens the immune system allowing TB infection to activate and turn into active TB disease. Individuals with both TB infection and HIV infection has a very high risk of developing active TB disease. Without treatment, these two infections can work together, to shorten the life span of the person infected with both.
- In patients with advanced HIV disease, there is no sufficient cell-mediated immune response to create cavitation and usually presents with lobar, pleural or disseminated disease.
- TB pleural effusion is exudative, lymphocyte-predominant, and contains high adenosine deaminase levels.
- TB pleural effusion occurs as a result of hypersensitivity reaction to M.tuberculosis, so pleural fluid smear is often negative for acid-fast bacilli and pleural biopsy is the gold standard for confirming the diagnosis.
- Treatment of HIV has to be delayed 1-2 weeks after TB treatment to avoid immune reconstitution inflammatory syndrome (IRIS).
Do all people with HIV get TB disease?
No, but it does increases the chance of getting TB disease if patient have both TB infection and HIV infection. For this reason, if patient have HIV infection, the doctor must also get a TB skin test.
What is the difference between latent TB infection and active TB disease?
TB is spread through the air from one person to another. The infectious droplets containing the mycobacteria are expelled into the air when a patient with TB disease of the lungs or throat coughs or sneezes. Individuals nearby may get exposed and inhale these mycobacteria and therefore they get infected. However, not everyone gets exposed and infected with TB mycobacteria becomes sick. As a result, two TB-related conditions exist: latent TB infection and active TB disease.
Most people who get exposed to TB mycobacteria and become infected are able to control the bacteria and stop them from growing. Consequently, the bacteria become inactive, but they remain dormant and alive in the body and can get activated later if the immune system is impaired and cannot control the growing of the mycobacterial infection. This is called latent TB infection. With impaired immune system, these mycobacteria begin to multiply in the body and cause active TB disease.
There are an estimated 9 to 14 million persons in the United States infected with TB bacteria. However, it has been reported that most people who have latent TB infection never develop active TB disease. In these people, the TB bacteria remain inactive for a lifetime without causing disease. Individuals with latent TB infection do not feel sick or spread TB mycobacteria to others. Since HIV affects the immune system, people with latent TB infection and HIV coinfection are at much higher risk of developing active TB disease. These mycobacteria begin to multiply in the body and cause active TB disease.