TUBERCULOSIS

TUBERCULOSIS - Katherine Berg, MD
BASICS
DESCRIPTION
Common disease transmitted by inhaling airborne bacilli from a person with active tuberculosis. Bacilli multiply in alveoli, are carried by macrophages, lymphatics, and blood to distant sites. Tissue hypersensitivity usually halts infection within 10 weeks.
• Latent infection
- Asymptomatic, with positive PPD
- Negative chest radiograph
- Noninfectious
• Active disease
- Occurs in 10% of infected individuals without preventive therapy
- Risk increases with immunosuppression and is highest within 2 years of infection
- 85% of cases are pulmonary, which is contagious.
• Primary: Disease resulting from initial infection.
• Recrudescent: Active disease occurring after period of latent, asymptomatic infection
• Miliary: Disseminated disease
• Systems Affected: Potentially any via hematogenous spread
ALERT
Pediatric Considerations
• Emphasize DOT (directly observed therapy)
• Caution with ethambutol
• Children on medication may attend school.
• Disseminated TB more common in infants; prompt treatment with 4 drugs if TB suspected
• Congenital infection may occur with miliary TB or endometrial TB in mother. If suspected, get PPD, chest radiograph, lumbar puncture, culture placenta in infant, then start treatment promptly.
• Consider BCG if unavoidable contact with TB
GENERAL PREVENTION
• Treat those with latent TB infection.
• Identify and test all close contacts of infected person.
• BCG vaccine: Live attenuated Mycobacterium bovis
- 50% efficacy preventing pulmonary disease, prevents 80% of TB meningitis and miliary disease in children
- In the US, consider BCG for children with negative PPD and HIV tests with unavoidable high risk, and for health care workers at high risk for drug-resistant infection (1).
- Used more commonly in countries where TB is endemic.
EPIDEMIOLOGY
• 1/3 of world's population infected with TB bacillus
• Higher incidence in ethnic minorities and medically underserved populations.
Incidence
• The Americas: 41 per 100,000
• Worldwide: 140 per 100,000
• In US, rate of decline of incidence slowing since 2000 (3.8% decrease per year as opposed to 7.1% per year in years 1993-2000)
Prevalence
• The Americas: 53 per 100,000
• Worldwide: 229 per 100,000
RISK FACTORS
• For infection
- Demographics: Homeless, minority
- Institutionalization (e.g., prison, nursing home)
- Close contact with infected individual
- Immigrant within 5 years (from Asia, Africa, Latin America, former Soviet Union states)
- Health care workers
• For development of disease once infected
- HIV; lymphoma; diabetes mellitus; chronic renal failure; cancer of head, neck, or lung
- Gastrectomy
- Steroids, immunosuppressive drugs
- IV drug abuse, malnutrition
ETIOLOGY
• Mycobacterium tuberculosis
• Mycobacterium bovis
• Mycobacterium africanum
ASSOCIATED CONDITIONS
HIV infection (emphasize DOT; most recommendations remain the same)