RespiratoryTier 2Disease (DEADMAN)

Tuberculosis

Description

Chronic granulomatous infection caused by *Mycobacterium tuberculosis*, primarily affecting the lungs but capable of involving almost any organ (extrapulmonary TB)

Low incidence in Australia (mostly in overseas-born individuals and specific high-risk communities) but a major global cause of infectious death; risk factors - HIV, immunosuppression (including biologics - screen before starting anti-TNF therapy), diabetes, malnutrition, incarceration, homelessness, close contact with an infectious case

Inhaled droplet nuclei -> alveolar macrophage infection -> primary infection (often asymptomatic, contained by cell-mediated immunity as a granuloma - "latent TB") -> reactivation (waning immunity - ageing, immunosuppression) or, less commonly, primary progressive disease (young children, immunocompromised)

Active pulmonary TB: chronic cough (>2-3 weeks), haemoptysis, weight loss, night sweats, fever; CXR - upper lobe cavitation classic for reactivation, primary disease often shows lower/mid-zone infiltrate +/- hilar lymphadenopathy
Sputum smear microscopy (AFB) + culture (culture is the gold standard, but slow - weeks); nucleic acid amplification testing (e.g. GeneXpert) gives rapid results and detects rifampicin resistance
Latent TB: tuberculin skin test (TST) or interferon-gamma release assay (IGRA) - neither distinguishes latent from active disease; a positive result needs CXR + clinical assessment to exclude active disease before treating as latent

Active TB - standard regimen: 2 months of rifampicin, isoniazid, pyrazinamide, ethambutol (2HRZE), then 4 months of rifampicin + isoniazid (4HR) - directly observed therapy (DOT) considered for adherence-risk patients
Latent TB - isoniazid monotherapy (6-9 months) or rifampicin-based shorter regimens, to prevent reactivation
Multidrug-resistant TB (resistant to at least rifampicin and isoniazid) requires specialist management with second-line agents for a longer duration
Notifiable disease - triggers public health contact tracing

HIV co-infection, immunosuppressive therapy (screen before biologics), diabetes, multidrug-resistant TB, latent TB reactivation

Without treatment, active pulmonary TB has substantial mortality; with appropriate multidrug therapy and adherence, cure rates are high - the principal driver of treatment failure is non-adherence/incomplete treatment, which also drives resistance

6 more sections, plus exam facts

Premium unlocks every note across every specialty, and the full exam fact library behind it.