Tuberculosis is a potentially severe infectious disease primarily affecting the lungs (pulmonary TB) but can also affect other parts of the body (extrapulmonary TB).
It is caused by the bacterium Mycobacterium tuberculosis.
Illustration of Tuberculosis, showing the effects of the bacterial infection on the lungs
Signs and Symptoms
1. Pulmonary TB:
Persistent Cough: Lasting more than three weeks, sometimes producing blood (hemoptysis).
Chest Pain: Painful breathing or coughing.
Fever and Chills: Often in the evening.
Night Sweats: Profuse sweating at night.
Weight Loss: Unintended weight loss and loss of appetite.
Fatigue: Persistent tiredness and weakness.
2. Extrapulmonary TB:
Lymphadenitis: Swollen lymph nodes.
Meningitis: TB infection of the brain lining, causing headaches, fever, and neurological symptoms.
Skeletal TB: Affects bones and joints, leading to pain and swelling.
Genitourinary TB: Involving kidneys, bladder, or reproductive organs.
Miliary TB: Disseminated TB affecting multiple organs.
Types of Tuberculosis
1. Based on Disease Location:
Pulmonary TB: Affects the lungs.
Extrapulmonary TB: Affects organs other than the lungs.
2. Based on Drug Resistance:
Drug-Sensitive TB: Responds to standard anti-TB drugs.
Multidrug-Resistant TB (MDR-TB): Resistant to at least isoniazid and rifampicin.
Extensively Drug-Resistant TB (XDR-TB): Resistant to isoniazid, rifampicin, any fluoroquinolone, and at least one second-line injectable drug.
Etiology
Causative Agent: Mycobacterium tuberculosis.
Transmission: Airborne, through inhalation of droplet nuclei from a person with active pulmonary TB.
Pathogenesis
Primary Infection:
Inhalation: M. tuberculosis enters the lungs.
Phagocytosis: Alveolar macrophages ingest bacteria, which survive and multiply inside macrophages.
Formation of Granulomas: Immune response forms granulomas to contain the infection, leading to latent TB.
Reactivation:
Immune Compromise: Reactivation of latent TB occurs when the immune system is weakened.
Active TB: Bacteria multiply, causing tissue damage and symptomatic disease.
Treatment
1. Standard Regimen for Drug-Sensitive TB:
Intensive Phase: 2 months of isoniazid, rifampicin, pyrazinamide, and ethambutol.
Continuation Phase: 4 months of isoniazid and rifampicin.
2. MDR-TB Treatment:
Longer Duration: 18-24 months with second-line drugs like fluoroquinolones and injectable agents (kanamycin, amikacin).
3. XDR-TB Treatment:
Complex Regimens: Often include bedaquiline, linezolid, and other newer drugs, lasting up to 24 months or more.
Supportive Care:
Nutritional Support: To counteract weight loss and malnutrition.
Management of Side Effects: Regular monitoring and management of drug side effects.
Isolation Measures: To prevent transmission until the patient is non-infectious.
Prevention:
BCG Vaccine: Administered in infancy in endemic countries.
Early Detection and Treatment: Active case finding, contact tracing, and treatment of latent TB.
Infection Control: Use of personal protective equipment (PPE) and proper ventilation in healthcare settings.