Overview
Definition
A highly contagious, chronic bacterial infection that primarily affects the lungs but can involve any organ system.
Epidemiology
One of the top 10 causes of death worldwide. High prevalence in developing countries, prisons, and homeless shelters.
Etiology & Risk Factors
- Mycobacterium tuberculosis (an obligate aerobe, acid-fast bacillus)
- Transmitted via airborne droplet nuclei (requires prolonged close contact)
Clinical Symptoms
- Chronic cough (often productive of purulent or blood-streaked sputum - hemoptysis)
- Fever (especially evening spikes)
- Night sweats
- Unexplained weight loss
- Fatigue and anorexia
Clinical Approach
Diagnosis
- Screening: Tuberculin Skin Test (PPD) or Interferon-Gamma Release Assay (IGRA / QuantiFERON Gold)
- Chest X-ray: Primary TB (Ghon complex/lower lobes), Reactivation TB (Apical cavitary lesions)
- Definitive Diagnosis: Sputum Acid-Fast Bacilli (AFB) smears (requires 3 samples) and mycobacterial culture (Gold Standard, takes weeks) or PCR
Management
- Latent TB: Isoniazid (INH) for 9 months OR Rifampin for 4 months
- Active TB (RIPE Therapy): Rifampin, Isoniazid, Pyrazinamide, and Ethambutol for 2 months, followed by INH and Rifampin for 4 more months
- Must supplement Vitamin B6 (Pyridoxine) with Isoniazid to prevent peripheral neuropathy
Complications
- Miliary TB (widespread hematogenous dissemination)
- Pott's Disease (TB of the spine)
- Massive hemoptysis (from Rasmussen's aneurysm)