Tuberculosis

Author: Dr. Veena

Tuberculosis is a disease that is becoming more common worldwide. This disease requires special attention and specialized laboratory techniques, such as microscopy and culture, to identify the responsible organisms. If tuberculosis (TB) is suspected, these tests must be specifically requested.

The impact of TB on world health is significant. In 2006, there were an estimated 9.2 million new cases, 14.4 million prevalent cases, and 1.5 million deaths attributable to TB. Furthermore, it is estimated that around one-third of the world’s population has latent TB.

TB is caused by infection with Mycobacterium tuberculosis (MTB), which is part of a complex of organisms including M. bovis (reservoir: cattle) and M. africanum (reservoir: humans). M. bovis infections occur due to the consumption of non-sterilized milk from infected cows. M. tuberculosis is spread through the inhalation of aerosolized droplet nuclei from other infected patients.

Primary Pulmonary TB:

Primary TB refers to the initial infection in a person who has not been previously affected. Some patients develop a self-limiting febrile illness, but clinical disease only occurs if there is a hypersensitivity reaction or progressive infection.

Factors that Increase the Chances of TB:

For the Patient: Children > young adults, close contact with a person having smear-positive pulmonary TB, smoking.
For the Disease: Chronic renal failure, malignancy, type 1 diabetes mellitus, deficiency of vitamins A and D.

Features of Primary TB:

Infection (4 to 8 weeks): Influenza-like illness.
Disease: Lymphadenopathy, cavitation, miliary TB, meningitis, pericarditis.

Hypersensitivity Reactions:

Erythema nodosum
Dactylitis
Phlyctenular conjunctivitis

Manifestations of TB Over Time:

3 – 8 weeks: Primary complex, positive tuberculin skin test.
3 – 6 months: Meningeal, miliary, and pleural disease.
Up to 3 years: Gastrointestinal, bone and joint, and lymph node disease.
Around 8 years: Renal tract disease.
From 3 years onwards: Post-primary disease due to reactivation or reinfection.