Tuberculosis Flashcards
Tuberculosis definition
infectious disease caused by Mycobacterium tuberculosis
Tuberculosis risk factors
- prolonged exposure
- birth in endemic country
- HIV, immunosuppression
- silicosis, apical fibrosis
Tuberculosis pathophysiology
- M. tuberculosis is inhaled
- engulfed by alveolar macrophages where it survives and grows
- kills macrophages and is released, travels to lymph nodes
- affected lymph node + region = Ghon
- TH1 response - T cells + macrophages form granuloma with necrotic centre
- latent infection - non-infective; can reactivate and cause miliary TB
Tuberculosis signs and symptoms
- cough
- fatigue
- weight loss
- night sweats
- clubbing
- haemoptysis
Latent TB diagnosis
- Mantoux test - 0.1ml of 1:1000 purified protein derivative injected intradermally; result 2-3 days later
- <6mm - negative, give BCG
- 6-15mm - previous BCG or TB infection
- > 15mm - positive, suggests TB
- false positive - miliary TB, sarcoidosis, HIV, lymphoma, <6mo old
Active TB diagnosis
- CXR shows upper lobe cavitation, bilateral hilar lymphadenopathy
- sputum smear - 3 samples, acid fast bacilli, 50-80% sensitive but less in HIV
- sputum culture - gold standard, 1-3 weeks in liquid medium
- NAAT - rapid diagnosis (within 48h), more sensitive than smear but less than culture
Tuberculosis management
Active TB:
- rifampicin & isoniazid for 6 months
- with pyridoxine (B6)
- pyrazinamide & ethambutol for 2 months
Latent TB:
- rifampicin + isoniazid for 3 months
- or isoniazid for 6m
Tuberculosis medication side effects
Rifampicin:
- liver enzyme inducer
- red urine
- hepatotoxicity
Isoniazid:
- peripheral neuropathy (give B6)
- agranulocytosis
- hepatotoxicity
- liver enzyme inhibitor
Pyrazinamide
- hyperuricemia causing gout
- arthralgia, myalgia
- hepatotoxicity
Ethambutol
- optic neuritis: check visual acuity before and during treatment
