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Pathophysiology of Pulmonary Tuberculosis

written by: DulceCorazon • edited by: dianahardin • updated: 10/29/2010

The pathophysiology of tuberculosis usually starts when a person inhales the infectious mycobacterium in the air. Those with weaker immune status may develop active TB, and those who are healthy may have the microorganism in their lung tissues, which can become active when their immunity lowers.

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    About Pulmonary Tuberculosis

    Pulmonary tuberculosis (PTB) is a highly contagious disease caused by bacterial infection of the lungs. The organism that causes PTB is known as Mycobacterium tuberculosis. Transmission of the disease is spread when a person with pulmonary tuberculosis sneezes or coughs, thus, releasing droplets into the air which is then breathed in by another person. Because of the ease of transmission of this disease, people are encouraged to learn the pathophysiology of pulmonary tuberculosis in order to know how to prevent its occurrence.

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    Stages of Infection

    There are three stages of infection in pulmonary tuberculosis - primary, latent, and active disease. People that have weak immune systems will usually exhibit symptoms of the disease one to two weeks after the microorganism enters the body. This is called primary infection. Tuberculosis-causing bacteria is normally killed by the body's immune system. Bacteria may also be absorbed by macrophages, or white blood cells. Such bacteria, however, can persist inside the macrophages and remain dormant for years, a condition that characterizes the latent infection stage.

    In nine out of ten affected individuals, the bacteria will no longer cause problems, but there is still the risk that the bacteria will multiply and cause tuberculosis later on, when the immune system weakens. In those with low immune status, PTB can become active and manifest with symptoms. For example, a person with a poor immune system, particularly those with acquired immune deficiency syndrome or AIDS, are prone to this. It is estimated that people with AIDS have a 5 to 10 percent chance of getting pulmonary tuberculosis if they are infected with the Mycobacterium tuberculosis.

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    Mycobacterium tuberculosis only lives among humans. The bacteria can be transmitted by a person who has pulmonary tuberculosis and is often spread through the air. So a person who touches a patient with pulmonary tuberculosis won’t usually get it by mere touch.

    People who have active pulmonary tuberculosis contaminate the air with Mycobacterium by sneezing, coughing or simply by talking. The mycobacterium tuberculosis can remain airborne for a couple of hours. When a person breathes the infected air, there is a good chance that the said person will develop tuberculosis in the lungs. It is thus recommended that people with active tuberculosis be isolated from other individuals to avoid transmission of the Mycobacterium tuberculosis.

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    The pathophysiology of pulmonary tuberculosis in the active stage often manifests with coughing. Many people who have been infected with the Mycobacterium tuberculosis may think that excessive coughing may be due to smoking, fever, cold and even asthma. The cough usually produces a tiny sputum colored green or yellow in the mornings. The sputum may eventually contain streaks of blood. Other symptoms of PTB include bouts of cold sweat, fever particularly at night, fatigue and weight loss. Some patients may also experience lack of appetite and lethargy.

    Individuals diagnosed with PTB are often given medications for about six to nine months, and may have to be isolated to prevent further spread of the disease in the community. Their family members may also be tested for the disease and given appropriate medications to avoid contracting the disease. Compliance with treatment is of utmost importance.

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    MedlinePlus: Pulmonary Tuberculosis,

    Merck Manuals: Tuberculosis,

    UMMC: Pulmonary Tuberculosis - Overview,