Tuberculosis (TB) - Emergency Medicine / ICU revision
Overview
Mycobacterium tuberculosis complex (principally M. tuberculosis) causes pulmonary and extrapulmonary disease.
TB remains an important consideration in acute care because it can present insidiously or as life‑threatening illness (respiratory failure, massive haemoptysis, tuberculous meningitis, miliary/disseminated disease) and because of its airborne transmission and public‑health implications.
UK practice is guided by NICE NG33 and UKHSA guidance; early isolation, specimen collection and liaison with local TB services are essential.
Pathogenesis and natural history
- M. tuberculosis is a slow‑growing, aerobic acid‑fast bacillus; culture and drug‑susceptibility testing (DST) take weeks.
- Outcomes after exposure:
- No infection (majority).
- Latent TB infection (LTBI): organism contained but viable; lifetime reactivation risk ≈ 5-10% (higher with immunosuppression).
- Active TB (primary or reactivation): pulmonary disease is most common; reactivation typically affects the lung apices.
- Miliary TB results from haematogenous spread and causes diffuse organ involvement (lungs, liver, spleen, bone marrow, CNS).
- Immunosuppression (HIV, steroids, transplant, diabetes, severe renal failure, malnutrition) raises the risk of extrapulmonary disease and dissemination.
Epidemiology and risk groups (clinical relevance)
- Higher risk groups: