Tuberculosis

Causes:

• The TB germs can only be transmitted by individuals who are currently infected. Speaking, sneezing, and even coughing can release the germs into the air, which can subsequently infect those who breathe it. If you live next to someone who has TB or if a room is poorly aired, this is more likely to occur. Once a person is infected, the bacteria will congregate in the lungs' air sacs and passageways, where they are typically kept in check by the immune system.
• If you are from one of the countries where TB is widespread or if you travel there, your risk of contracting the disease is increased. Elderly persons, those who are homeless, those who use drugs excessively, people who have served time in a penal facility, and those whose immune systems have been compromised by HIV or AIDS are among those who are more susceptible to contracting TB (acquired immune deficiency syndrome). Naturally, the chances rise if you are in close or regular contact with someone who is exhibiting active TB symptoms. This is particularly valid for healthcare professionals who might come into contact with patients who have active TB.
• When a person has an inactive TB infection, the following variables may contribute to the promotion of active disease:
  • Diabetes
  • head or neck cancer
  • illnesses that suppress the immune system, such as HIV or AIDS
  • kidney disease
  • Long-term steroid use
  • Malnutrition
  • Medications that suppress the immune system, such as anticancer medications (e.g., cyclosporine, tacrolimus)*
  • Pregnancy
  • Radiotherapy

Predisposing factors:

• Age:
  • The placentas with the infection may spread to the fetus. Similar to this, uncommon cases might be congenital. However, as a child gets older, the likelihood of contracting tubercle bacilli infections increases gradually.
• Sex:
  • During puberty, the adolescent girls are susceptible to developing active TB.
• Malnutrition
• Environment:
  • Children who live in overcrowded apartments, hostels, or camps with poor ventilation, damp conditions, and unclean and unhygienic conditions are at a high risk of developing tuberculosis.
• Low socio-economic status
• Low immunity

Mycobacterium tuberculosis, which causes tuberculosis, is an infectious bacterial disease that most frequently affects the lungs. Droplets from the throat and lungs of patients with the active respiratory disease are used to transmit it from one person to another.

Less than 10% of people with M. tuberculosis have latent TB infections, also known as LTBI, which are asymptomatic and have no likelihood of developing into overt, active tuberculous disease. The chance of having active TB in people with HIV rises to over 10% year. The fatality rate for active TB individuals might reach 66% if proper treatment is not provided.

When the mycobacteria enter the pulmonary alveoli, where they infiltrate and multiply inside alveolar macrophage endosomes, the TB infection starts. Macrophages recognize the bacterium as being alien and make an effort to phagocytose it. During this process, the macrophage encloses the bacterium and briefly stores it in a phagosome, a membrane-bound vesicle. A phagolysosome is produced once the phagosome joins forces with a lysosome. The cell tries to kill the bacterium in the phagolysosome by using acid and reactive oxygen species. But M. tuberculosis is shielded from these poisons by a thick, waxy mycolic acid capsule. In the macrophage, M. tuberculosis can reproduce and eventually destroy the immune cell.

The "Ghon focus," the main lung infection location, is typically found in the upper half of the lower lobe or the lower part of the upper lobe. Lung tuberculosis can also develop as a result of bloodstream infection. The top of the lung is often where one may locate a Simon focus. [56] This hematogenous transmission can also spread an infection to further-reaching areas, including the kidneys, bones, brain, and peripheral lymph nodes. The disease can affect any part of the body, but for unknown reasons, it rarely affects the thyroid, pancreas, skeletal muscles, or heart.

One of the granulomatous inflammatory disorders is tuberculosis. Granulomas are formed by the aggregation of macrophages, T lymphocytes, B lymphocytes, and fibroblasts. Lymphocytes surround the infected macrophages. In the alveolar lumen, a massive multinucleated cell is created when other macrophages attack the infected macrophage. The granuloma may stop mycobacteria from spreading and offer a local habitat for immune system cell engagement. The bacteria may employ the granulomas, according to more recent research, to protect themselves from the host's immune system. The immune response is inhibited because macrophages and dendritic cells in the granulomas cannot present antigen to lymphocytes. Latent infection can develop from bacteria that become dormant inside the granuloma. The development of aberrant cell death (necrosis) in the center of tubercles is another characteristic of the granulomas. Caseous necrosis is the medical word for this condition, which has a texture similar to soft, white cheese.

The TB bacteria can travel throughout the body and create several foci of infection if they are able to enter the bloodstream through a site of damaged tissue. These foci of infection will all show as little, white tubercles in the tissues. Miliary tuberculosis is the name for this severe form of TB disease, which is particularly prevalent in young children and people with HIV. Even with treatment, the mortality rate for those with this disseminated TB is significant (about 30%).

The virus fluctuates in severity among various persons. Healing and fibrosis frequently counteract tissue degeneration and necrosis. Scarring and cavities filled with caseous necrotic debris replace the damaged tissue. Some of these cavities are connected to the bronchi during an active disease, which makes it possible to cough up this substance. It can spread the infection since it has active bacteria. The use of the proper antibiotics during treatment eliminates bacteria and promotes recovery. After treatment, scar tissue eventually replaces the damaged areas.