What happens in Tuberculosis?

 

 " For millennia, our ancestors have suffered and died with

tuberculosis, without knowing what it was, what caused it, or

how to stop it. Today, we have knowledge and tools they could

only have dreamed of. We have political commitment, and

we have an opportunity that no generation in the history of

humanity has had: the opportunity to write the final chapter

in the story of TB"

 

By-Dr Tearos Hananom Ghebreyesus

Director-General

World Health Organization

Do you know that TB remained the world’s second-leading cause of death from a single infectious agent in 2022, after COVID-19, and caused almost twice as many deaths as HIV/AIDS, according to WHO reports.But many people have no idea what tuberculosis (TB) is or what happens in cases of tuberculosis (TB). All of us have a vague idea of TB, but almost nobody has ever thought about what happens in TB, how it causes the disease, or death. 

And TB is not a simple disease that you can ignore; it is infectious, community-based, and spreads, so you should be careful and have information about this type of disease.   

So , keep reading , i am going expain how these diseases or conditions affect the normal functioning of the body. It's about understanding the mechanisms behind why and how diseases develop and progress within the body.

What happens in Tuberculosis? 

Tuberculosis, or more commonly, TB, is caused by a bacteria called Mycobacterium tuberculosis. This bacteria, when inhaled, goes to the respiratory tract and forms a cavity; thus, we have tuberculosis. But it's not that simple; I am going to explain the full mechanism. 

Before this, if you want to know

How our body protect us from Pathogens?

 

Certainly, Mycobacterium tuberculosis has a very dangerous property: it can inhibit phagolysosomes. This phagolysosome basically helps in the phagocytosis process of our immune cells, i.e., WBCs, macrophages, etc. So, our immune cells could not kill the bacteria as effectively as possible. 

So, what happens is that when bacteria come into our system, they are first encountered by macrophages, but macrophages cannot kill them due to the inhibition of phagolysosomes. These macrophages release some cytokines or signals, which attract more macrophages, T lymphocytes, and other immune cells. These immune cells surround the bacteria and form a granuloma.

This granuloma causes necrosis of lung tissues (caseous necrosis), which leads to the formation of a cavity in the lungs.

Most commonly, the bacteria affect the right middle lobe or right lower lobe of our lungs in our first encounters. 

But this can migrate to other parts of our body, like the lymph node, called hilar lymphodenopathy.

But there is a catch: 

In most of the cases of TB (approximately 90%), the disease goes into a latent phase (dormant phase) or does not show any symptoms initially, but when the person becomes immunocompromised, like in the case of HIV, post-transplantation period, alcohol abuse,old age, etc., it gets reactivated or starts replication.

So, what happens? This reactivated bacteria travels from the lower lobe to the upper lobe due to increased oxygen demand, where they cause a lot of consolidation, which leads to fibrotic necrosis of the upper lobes and forms lesions.

What's about 10% remaining,  they directly leads to consolidation, for them there is no dormant phase.

These consolidations can leads to mainly three complications i.e 

• Pneumothorax- It is a condition characterized by the presence of air or gas in the pleural space, the area between the lungs and the chest wall. When these consolidations irritates the plural cavity and rupture it then air enters the pleural space, it can cause the lung to collapse partially or completely, leading to symptoms such as sudden chest pain, shortness of breath, and sometimes, a feeling of chest tightness.
• Bronchopneumonia- It is a kind of pneumonia that primarily affects the bronchioles and surrounding lung tissue. It typically occurs as a result of the spread of infection from the airways (bronchi and bronchioles) to the surrounding lung tissue.
• Plural effusion- It is a condition characterized by an abnormal accumulation of fluid in the pleural space, the space between the layers of the pleura, which are the membranes lining the lungs and the inner chest wall.

These fibrocasius cavities can cause the lung vessels to rupture, which leads the blood to the bronchia and cause hemoptysis (blood in the caugh).

It also inflames the airways, which causes excessive coughing. 

The immune cells also release cytokines, or signals,which stimulate the hypothalamus. This causes fever, night sweats, and weight loss.

The above explanation is all about pulmonary tuberculosis. But tuberculosis can be extrapulmonary when it travels to other parts of the body through the blood.

• Meningitis (Brain)
• Scrafula (cervical lymph node)
• Constrictive pericarditis (heart)
• Hepatitis (Liver)
• Increased WBC in Urine-Pyuria (Kidney)
• Adrenal crises/Addison disease (Adrenal gland)
• Pott's disease (Lumber vertebra)
• Osteomyelitis (Bones)

Tuberculosis (TB) primarily spreads through the air when an infected person with active TB disease coughs, sneezes, speaks, or sings, releasing tiny droplets containing the bacteria into the air. When another person inhales these droplets, they can become infected with TB.

That's why this type of infection is more common in people with a high exposure rate, like in 

• Prison
• Healthcare Facilities 
• Area with high population density

According to WHO, around 9. 6 million people got affected by Tuberculosis (TB) in 2014 and 1.5 million died because of it. In worldwide TB is now rank alongside HIV as a leading cause of death. So, be informed.

This is a brief explanation of Tuberculosis pathophysiology, or what happens in case Tuberculosis. 

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