Pathophysiology of Pulmonary Tuberculosis
Introduction
Pulmonary tuberculosis (TB) is an infectious disease caused by the bacterium Mycobacterium tuberculosis. It primarily affects the lungs, but can spread to other organs. This presentation will delve into the pathophysiology of pulmonary TB, exploring the mechanisms behind its development and progression.
1. Transmission and Infection
- Inhalation: TB is spread through the air when an infected person coughs, sneezes, speaks, or sings.
- Droplet nuclei: These tiny particles containing the bacteria remain suspended in the air for long periods.
- Inhalation: When inhaled, the bacteria reach the alveoli.
- Macrophages: Alveolar macrophages engulf the bacteria, attempting to contain the infection.
2. Primary Infection
- Dormant state: In most cases, the immune system successfully controls the infection, preventing disease. The bacteria remain dormant within macrophages, forming granulomas.
- Granuloma formation: Macrophages, lymphocytes, and other immune cells surround the infected cells, forming a wall around the bacteria.
3. Latent TB Infection
- No symptoms: Individuals with latent TB infection show no symptoms and are not contagious.
- Risk of reactivation: However, they carry the risk of the bacteria becoming active and causing disease later.
4. Active TB Infection
- Reactivation: Factors such as weakened immune system, HIV infection, malnutrition, or certain medications can trigger reactivation.
- Cell-mediated immunity: In active TB, the immune response becomes ineffective, allowing the bacteria to multiply.
- Caseous necrosis: The center of the granuloma breaks down, forming a cheese-like substance.
- Cavitation: The necrotic tissue may liquefy and form cavities in the lungs, releasing bacteria into the airways and spreading the infection.
5. Clinical Manifestations
- Cough: Persistent cough, often with phlegm.
- Fever: Low-grade fever, especially in the evening.
- Night sweats: Excessive sweating at night.
- Weight loss: Unexplained weight loss.
- Fatigue: Persistent tiredness and weakness.
- Chest pain: Pain in the chest, especially when breathing.
- Hemoptysis: Coughing up blood.
6. Complications
- Miliary TB: Widespread dissemination of the bacteria throughout the body.
- Tuberculous meningitis: Infection of the brain and meninges.
- Tuberculous pleurisy: Inflammation of the lining of the lungs.
- TB-associated renal disease: Infection of the kidneys.
7. Diagnosis and Treatment
- Diagnosis: Chest X-ray, sputum smear microscopy, culture, and molecular tests are used to diagnose TB.
- Treatment: Anti-tuberculosis medications are used to treat TB. A combination of drugs is typically used to prevent drug resistance and ensure the eradication of the bacteria.
8. Prevention and Control
- Vaccination: The Bacille Calmette-Guérin (BCG) vaccine can provide partial protection against TB.
- Early detection and treatment: Prompt diagnosis and treatment of TB cases are essential to prevent further spread.
- Public health measures: Contact tracing and isolation of infected individuals are crucial in controlling TB outbreaks.
Conclusion
Pulmonary TB is a serious infectious disease that can have devastating consequences. Understanding the pathophysiology of the disease is crucial for effective diagnosis, treatment, and prevention. By recognizing the stages of infection, the mechanisms of bacterial spread and the development of granulomas, we can better control the disease and minimize its impact on individuals and communities.
