Question

What is the pathophysiology of tuberculosis, in your own words?

Answer 1

PATHOPHYSIOLOGY OF TUBERCULOSIS

Inhalation of Mycobacterium tuberculosis leads to one of four possible outcomes :

1. Immediate clearance of the organism.

2. Latent infection.

3. The onset of active disease (Primary disease).

4. Active disease many years later (Reactivation disease).

* PRIMARY DISEASE

The tubercle bacilli establish infection in the lungs after they are carried in droplets small enough (5 to 10 microns) to reach the alveolar space. If the defence system of the host fails to eliminate the infection, the bacilli proliferate inside alveolar macrophages and eventually kill the cells. The infected macrophages produce cytokines and chemokines that attract other phagocytic cell, including monocytes, other alveolar macrophages and neutrophils, which eventually form a nodular granulomatous structure called the Tubercle. If the bacterial replication is not controlled, the tubercle enlarges and the bacilli enter local draining lymph nodes. This leads to lymphadenopathy, a characteristic clinical manifestation of primary tuberculosis (TB).

* REACTIVATION DISEASE

Reactivation TB results from proliferation of a previously dormant bacterium seeded at the time of the primary infection.

Other condition that facilitate reactivation include :

1. Diabetes.

2. Head and neck cancer.

3. Gastrectomy.

4. Jejunoileal bypass surgery.

5. Dialysis - dependent Chronic Kidney disease.

6. Significant weight loss.

7. Drugs that suppress the immune system.