Tuberculosis

Question 1

Describe the pathophysiology of TB?

Answer 1

• Infection by Mycobacterium tuberculosis
• Active infection occurs
• Latent TB can occur later

Question 2

Describe tha active infection of TB?

Answer 2

• Immune system response is inadequate
• Can arise from primary infection or re-activation
• Transmitted via inhaled droplets
  
  • Only pulmonary disease is communicable

Question 3

Describe latent TB?

Answer 3

• Infection without disease due to persistent immune containment
  
  • Granuloma formation to prevent growth
• Positive skin/blood testing
• Risk factors for reactivation
  
  • HIV, organ transplant, immunosuppression, high-risk settings

Question 4

SITES OF TB

Answer 4

Question 5

Name the systemic features of TB?

Answer 5

• Low-grade fever
• Anorexia, weight loss
• Night sweats, clubbing, erythema nodosum

Question 6

Describe the clinical features of pulmonary TB?

Answer 6

• Cough for >3 weeks
  
  • Dry then productive
• Pleurisy, haemoptysis, pleural effusion
• Aspergilloma may form in cavities

Question 7

Describe Miliary TB?

Answer 7

• Haematogenous dissemination
  
  • Leads to formation of discrete foci of granulomatous lung tissue
  • Millet seed appearance on CXR

Question 8

Describe the features of skin TB?

Answer 8

• Lupus vulgaris
  
  • Persistent red-brown ‘apple-jelly’ nodules
• Scrofuloderm
  
  • Skin lesion

Question 9

Answer 9

Lupus vulgaris

Question 10

Answer 10

Scrofuloderma

Question 11

Describe the diagnostic tests for latent TB?

Answer 11

• Tuberculin skin testing (TST) - Mantoux test
  
  • Inject tuberculin into skin
  • Size of induration determines positivity
• Interferon-gamma release assays (IGRAS)
  
  • Measure interforn-gamma release from T-cells reacting to TB antigen

Question 12

Describe the diagnostic tests for Active pulmonary TB?

Answer 12

• CXR
  
  • Opacities in upper lobe (typically)
  • Cavitation, calcification, miliary disease
• Sputum smear
  
  • Stained for acid-fast bacilli (AFB)
• Sputum culture (several weeks for result)
• NAAT
  
  • Direct detection of M. tuberculosis in spurum by DNA/RNA amplification

Question 13

Describe the diagnostic tests for Extra-pulmonary TB?

Answer 13

• Investigate for coexisting pulmonary disease
• Obtain material from aspiration or biopsy for AFB staining/ culture
• NAAT on any sterile body fluid (CSF, pericardial fluid)

Question 14

What antibiotics can be used for treating TB?

Answer 14

• Rifampicin
• Isoniazid
• Pyrazinamide
• Ethambutol

Question 15

Describe Rifampicin?

Answer 15

• Enzyme induced
• Care with warfarin, osetrogens, phenytoin
• Secretions stained orange (inc contact lens)
• Altered liver function

Question 16

Describe Isoniazid?

Answer 16

• Inhibits formation of active pyridoxine (vit B6)
  
  • Causes peripheral neuropathy
• Give with prophylactic pyridoxine
• Can cause hepatitis

Question 17

Describe Pyrazinamide?

Answer 17

• Idiosyncratic hepatotoxicity
• Reduce dose if eGFR <30

Question 18

Describe Ethambutol?

Answer 18

• SEs: colour blindness, reduced visual acuity, optic neuritis
• Monthly vision check after 2 months