Simple Pathophysiology of Pulmonary Tuberculosis
Tuberculosis (TB) is a contagious disease caused by the bacterium Mycobacterium tuberculosis. It primarily affects the lungs, but can also spread to other parts of the body. Here's a simple explanation of the pathophysiology of pulmonary TB:
Infection and Initial Response
- Inhaling infected droplets: The infection begins when a person inhales tiny droplets containing M. tuberculosis expelled through coughs or sneezes from an infected individual.
- Reaching the alveoli: These droplets travel down the respiratory tract, reaching the alveoli (tiny air sacs in the lungs) where they lodge.
- Immune response: The body's immune system, specifically macrophages, tries to engulf and destroy the bacteria.
- Formation of granulomas: In some cases, the immune system can successfully eliminate the bacteria. However, if M. tuberculosis survives, it can stimulate the formation of granulomas. These are small, localized areas of inflammation containing macrophages, lymphocytes, and infected cells.
Progression of Disease
- Latent TB: In many cases, the immune system can contain the infection, preventing it from spreading further. This is called latent TB, and the individual does not experience symptoms or have contagious bacteria.
- Active TB: If the immune system is weakened or the bacteria are particularly virulent, the infection can reactivate and progress to active TB.
- Breakdown of granulomas: The bacteria can begin to multiply and cause the granulomas to break down, releasing bacteria into the surrounding tissues.
- Cavitation: As the infection progresses, the damaged lung tissue can form cavities (open spaces) in the lungs. These cavities can make it difficult to breathe and can also serve as reservoirs for the bacteria, facilitating transmission to others.
- Spread to other organs: In severe cases, the bacteria can spread from the lungs to other parts of the body through the bloodstream, causing extrapulmonary TB.
Symptoms of Pulmonary TB
Symptoms of active TB include:
- Coughing: This is often persistent and can produce phlegm, sometimes streaked with blood.
- Chest pain: Pain in the chest may occur when breathing or coughing.
- Fatigue: Feeling tired and weak is a common symptom.
- Weight loss: Unexplained weight loss is a sign of active TB.
- Fever: Low-grade fever is also common.
- Night sweats: Sweating excessively at night can be another symptom.
- Loss of appetite: A decrease in appetite is often associated with TB.
Conclusion
Understanding the pathophysiology of pulmonary TB helps us appreciate the complex interplay between the bacteria and the immune system. It highlights the importance of early detection and treatment to prevent the spread of infection and mitigate the effects of the disease.
