Tuberculosis is caused by a bacterium called Mycobacterium Tuberculosis. Tuberculosis is an infectious disease that primarily affects the respiratory system, but it can also affect other systems, such as the gastrointestinal system, musculoskeletal system, nervous system, etc. It may be present as a latent or an active infection. Active cases can be presented with symptoms like cough, hemoptysis (blood in the sputum), fever, weight loss, etc.

Other names

Also known as TB, Koch’s Disease

Causes Of Tuberculosis

  • Tuberculosis is caused by a bacterium called Mycobacterium tuberculosis.

  • TB usually spreads from one person to the other through the air.

  • When a person suffering from TB sneezes, coughs or spits, the bacteria gets into the air.

  • Hence, when a person inhales even a few of these bacteria from the air, he/she becomes infected.

  • Although it is contagious, the bacteria grows at a slow rate and requires you to spend considerable time around the person who is sick.

  • This means, it requires close and prolonged contact with a person who has active tuberculosis.


Symptoms of Pulmonary TB

Tuberculosis most commonly affects the lungs and can cause the following symptoms:

  • Coughing that lasts for more than 2 weeks with or without fever

  • Fever, especially an evening rise in body temperature

  • Presence of blood in the sputum

  • Chest pain

  • Loss of appetite

  • Loss of weight

  • Chronic fatigue

  • Night sweats and chills

Symptoms of TB other than pulmonary TB :

Occasionally, tuberculosis may also affect other organs, such as bones, stomach, etc., and presents with common symptoms like fever, weight and appetite loss and some specific symptoms related to organ system involved like :

  • Bone TB involving the spine can cause back pain and neurological complications like paraplegia where the lower limbs become paralyzed.

  • Gastrointestinal system disease can cause nausea, vomiting, diarrhea, malabsorption etc.

  • Tuberculosis of the kidneys can cause blood in the urine.

  • Infection involving the brain and its covering membrane can cause seizures, headaches, neurological abnormalities, etc.


There are 5 different types of tuberculosis based on the type of infection. These include:

Latent tuberculosis

Latent tuberculosis does not cause any symptoms as the body’s immune system keeps the infection at bay. In latent tuberculosis, the person carries the bacteria but does not develop any symptomHowever, there is a possibility that the latent infection may reactivate at a later stage in life when the body’s immune defenses go down and may lead to active disease.

Active tuberculosis

Active tuberculosis refers to a condition where the bacteria are in an active stage and cause symptoms. Active tuberculosis can be further classified into pulmonary and systemic tuberculosis. Although tuberculosis is primarily a disease of the lungs (pulmonary TB), it may affect other organs in the body, such as bones, lymph nodes, brain, kidneys, intestine, and reproductive system. When active tuberculosis is present in other parts of the body, it is known as systemic tuberculosis.

Disseminated tuberculosis

Also known as miliary tuberculosis, this is a severe type of infection where the tuberculosis bacteria spread to the entire body through the bloodstream.

Multidrug resistant tuberculosis (MDR TB)

This type of tuberculosis is caused by a bacteria which is resistant to at least two most common and potent drugs used to treat TB namey isoniazid and rifampin.

Extensively drug resistant tuberculosis (XDR TB)

This is a rare type of tuberculosis in which the bacteria is resistant to more than two drugs used to treat TB. In addition to isoniazid and rifampin, people suffering from XDR TB are resistant to fluoroquinolones (an antibacterial medicine) and at least one of three injectable second-line drugs used to treat bacteria.

Risk factors

Although all age groups are at risk of TB, the risk is higher in people who:

  • Live in or travel to a country with a higher prevalence of tuberculosis such as tropical and developing countries.

  • Work in places constantly exposed to crowds, such as hospitals, community centers, prisons, etc.

  • Suffer from malnourishment. It is seen that undernourished people are 3 times more at risk of TB as compared to healthy people.

  • Suffer from diabetes or are on medicines such as steroids or anti-cancer drug therapy.

  • Suffer from weakened immunity or are recovering from an illness.

  • Are infected with HIV/AIDS as the risk of getting tuberculosis is 18 times higher for patients with HIV.

  • Consume excess alcohol and smoke tobacco products.


Laboratory tests

Blood Tests

  • Cartridge based nucleic acid amplification test (CB-NAAT) is a rapid molecular test that helps to detect TB.

  • It not only identifies the bacteria responsible for TB but also helps to find rifampicin resistance bacteria within two hours.

  • It is recommended by WHO as an initial diagnostic test to check for TB in suspected cases of pulmonary and other forms of TB, especially in children.

  • TB Platinum Interferon Gamma Release Assay is used to check for the body’s immune response to the tuberculosis bacteria.

  • Other tests such as Complete Blood Count, Erythrocyte Sedimentation Rate are performed to evaluate the body’s response to infection.

  • HIV 1 And 2 Antibody. As tuberculosis is highly associated with HIV, doctors usually check for the likelihood of HIV exposure when tuberculosis is suspected.

Sputum analysis

Sputum samples are analyzed using tests like stain AFB (ZN Stain), sputum, and Mycobacterium tuberculosis DNA PCR - Qualitative -Sputum. These tests help to check for the presence of tuberculosis bacteria in the sputum. A positive test confirms the diagnosis of tuberculosis.

Skin prick test

  • This is also known as the Mantoux test. It is a screening test used to determine a person’s risk of TB infection or the risk of the progression of the disease, if infected.

  • For this, a small amount of tuberculin is injected into the skin.

  • If swelling or reaction occurs at the site of injection within 48-72 hours, it is considered a positive test and indicates exposure to the tuberculosis bacteria.

  • False-positive test results are possible if the person has been vaccinated for tuberculosis recently.

Imaging studies

In pulmonary tuberculosis cases, imaging studies like X-Ray chest PA View, HRCT chest - plain are required to evaluate the extent of the disease in the lungs. In extrapulmonary tuberculosis cases, other imaging studies, such as X-Ray dorsal spine AP & lateral view, MRI brain, etc., may be done as appropriate.

diseases treatments health prevention tuberculosis respiratory-system mycobacterium-tuberculosis

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