Pulmonary Tuberculosis
An airborne bacterial infection caused by M. tuberculosis that primarily affects the lungs, leading to granulomatous inflammation, cavitary lesions, and chronic respiratory symptoms.
Emergency Management: Massive Hemoptysis: Secure airway, place patient in lateral decubitus position (bleeding side down), consult interventional radiology for bronchial artery embolization.
Pulmonary tuberculosis is a highly contagious, chronic bacterial infection of the lungs caused by Mycobacterium tuberculosis. It typically presents as a necrotizing granulomatous inflammation with caseation. The disease can be latent (asymptomatic and non-infectious) or active, leading to progressive pulmonary destruction and potential extrapulmonary dissemination.
Detailed Overview
Tuberculosis remains one of the top infectious disease killers worldwide, transmitting via inhalation of aerosolized droplet nuclei. Once inhaled, alveolar macrophages ingest the bacilli, which evade destruction and multiply, forming a Ghon focus. Cell-mediated immunity halts the infection in most individuals, resulting in latent TB infection (LTBI). However, roughly 5-10% of infected individuals will develop active TB, often due to immunocompromise (e.g., HIV, TNF-alpha inhibitors), malnutrition, or aging, leading to classic symptoms of chronic cough, hemoptysis, and cavitary lung lesions.
Epidemiology & Demographics
In 2021, approximately 10.6 million people fell ill with TB globally, with 1.6 million deaths. Incidence is highest in South-East Asia, Africa, and the Western Pacific. Male to female ratio is ~1.5:1. HIV co-infection occurs in about 8% of incident cases.
Etiological Mechanism
The sole causative agent is Mycobacterium tuberculosis, a slow-growing, obligate aerobic, acid-fast bacillus (AFB) characterized by a lipid-rich cell wall containing mycolic acids.
Primary Causes
Mycobacterium tuberculosis infection
Inhalation of M. tuberculosis droplet nuclei leads to phagocytosis by alveolar macrophages. The bacilli prevent phagolysosome fusion through sulfatides and cord factor, multiplying intracellularly. A Th1-mediated immune response ensues, secreting IFN-gamma which activates macrophages to form epithelioid cells and multinucleated Langhans giant cells, enclosing the bacilli in a granuloma (tubercle) with a caseous, necrotic center. In active pulmonary TB, caseous material liquefies and empties into the bronchial tree, creating cavities and allowing for aerogenic spread.
Diagnostic Criteria & Guidelines
Confirmed by isolation of M. tuberculosis complex from respiratory secretions via culture or Nucleic Acid Amplification Test (NAAT/Xpert MTB/RIF). AFB smear provides presumptive evidence.
Intensive phase (2 months): Isoniazid (INH) 300 mg PO daily, Rifampin (RIF) 600 mg PO daily, Pyrazinamide (PZA) 1000-2000 mg PO daily, and Ethambutol (EMB) 800-1600 mg PO daily. Continuation phase (4 months): Isoniazid and Rifampin daily. (Total 6 months regimen). Pyridoxine (Vit B6) 25-50 mg daily is added to prevent INH neuropathy.
Second-Line & Adjunctive Therapy
For Multi-Drug Resistant TB (MDR-TB): Regimens including Bedaquiline 400 mg daily for 2 weeks then 200 mg 3x/week, Linezolid 600 mg daily, Levofloxacin 750 mg daily, and Clofazimine for 6-9 months.
Surgical & Procedural Management
Rarely indicated today, but lobectomy/pneumonectomy may be considered for localized multidrug-resistant disease or massive refractory hemoptysis.
Patient Counseling & Advice
Emphasize absolute adherence to the full 6-month treatment course to prevent relapse and development of drug-resistant TB. Warn about rifampin turning urine and tears red-orange.
Follow-Up & Monitoring Schedule
Monthly sputum smears and cultures until two consecutive cultures are negative. Baseline and monthly hepatic panels (AST, ALT, Bilirubin) to monitor for drug-induced hepatotoxicity.
Preventive Strategies
BCG vaccination in endemic countries. Treatment of LTBI with Isoniazid 300 mg daily for 9 months or Isoniazid+Rifapentine weekly for 3 months to prevent progression to active TB.
Excellent if fully susceptible and patient is adherent to therapy (cure rates >95%). Untreated active TB has a 50% mortality rate within 5 years.