Tuberculosis

Question 1

Define tuberculosis

Answer 1

Granulomatous infectious disease caused by Mycobacterium tuberculosis
Most commonly involves the lungs but may also affect the lymph nodes (scrofula), CNS (tuberculous meningitis), liver, bones (spinal TB - Pott’s disease), GU tract and GI tract

Question 2

What are the types of TB?

Answer 2

Primary TB – initial pulmonary infection
Post-primary TB – reinfection or reactivation
Miliary TB – haematogenous dissemination

Question 3

What are the causes/risk factors of TB?

Answer 3

Infection requires inhalation of droplet nuclei -> alveolar deposition -> bacteria are engulfed by alveolar macrophages -> intracellular multiplication -> bacteria kill macrophages -> release of bacteria -> immune response -> clearance, persistent latent infection or progression to primary disease
• Close TB contacts
• Immunocompromised e.g. HIV infection
• Endemic regions

Question 4

What are the symptoms of TB?

Answer 4

• Cough
• Fever
• Anorexia
• Weight loss
• Malaise
• Night sweats
• Pleuritic chest pain
• Haemoptysis
• SOB

Question 5

What are the signs of TB?

Answer 5

• Crackles
• Bronchial breath sounds
• Fibrosis
• Pleural effusion
• Clubbing
• Erythema nodosum

Question 6

What are the investigations for TB?

Answer 6

• Sputum MC&S – at least 3 samples
o Microscopy with Ziehl-Neelsen stain –
acid fast bacilli
o Culture on Lowenstein-Jensen medium;
takes <6 weeks
o Low sensitivity
• Tuberculin skin tests (Mantoux and Heaf) +ve in
previous exposure to M. TB or BCG
• Interferon gamma release assays – diagnose
latent TB (interferon released when T cells are
exposed to TB antigens)
• CXR
o Primary: peripheral consolidation, hilar lymphadenopathy
o Post-primary: upper lobe shadowing, cavitation, calcification
o Miliary: reticulonodular shadowing

Question 7

What is the management for TB?

Answer 7

RIPE (R+I for 6 months, P+E for 2 months)
• Rifampicin – SE orange bodily fluids, P450 enzyme inducer
• Isoniazid – SE peripheral neuropathy (give pyridoxine – B6)
• Pyrazinamide – SE hepatotoxicity, gout
• Ethambutol – SE optic neuropathy (esp. colour vision)