Tuberculosis

Question 1

What is TB

Answer 1

TB is an infectious disease caused by mycobacterium TB. It primarily affects the lungs, but disease can occurs in CNS, liver, bones, GI/GU tracts

Question 2

Describe pathogenesis of TB infection

Answer 2

inhalation of TB pathogen

TB is detected by macrophages in lungs and a lung lesion called Ghon complex develops (lung lesion with hilar lymph nodes)

TB can remain dormant in macrophages in lungs in immucompetent people (95%) and Ghon complex heals by fibrosis

5% get reactivation of TB causing cavitary TB and miliary disease e.g. in CNS, vertebral bodies ,kidneys, lymph nodes

Question 3

What are risk factors for TB reactivation?

Answer 3

Immunocompromised
Kids
HIV malnutrition

Question 4

What areas of lung does reactivation typically affect?

Answer 4

Lung apices, can then spread to local or distant sites

Question 5

What are Sx of TB?

Answer 5

low grade fever
anorexia
weight loss
malaise
night sweats
clubbing

pulmonary: coughing, pleurisy, haemoptysis SOB

Question 6

What are risk factors for TB?

Answer 6

Exposure to infection
Birth in an endemic country
Immunosuppression
Silicosis
Malignancy
HIV

Question 7

What Ix for TB?

Answer 7

CXR: fibronodular opacities in upper lobes, with or without cavitation

• May be calcification
• Ghon complexes are evidence of old TB
• Miliary TB will show as discrete foci or granulomatous tissue throughout the lung

TB TESTS:

Sputum AFB: grade from 1+ to 4+

NAAT: if AFB is +ve, can confirm that the mycobacteria is TB

Culture: takes 8 weeks to grow

OTHER

BAL and bronchoscopy: done if sputum induction is unsuccessful and other tests are negative with suggestive history.

Question 8

What is miliary TB?

Answer 8

Massive lymph/haem dissemination of TB throughout the body and organs

Question 9

What Ix looking for latent TB?

Answer 9

Mantoux test: inject antigens (tuberculin) into arm and see if there is a reaction, suggesting previous exposure. Measure it. Type IV hypesensitivity reaction (delayed)

T spot test (Quantiferon): expose blood to TB and see how much IFN gamma is made by T cells

Question 10

What are DDx for TB?

Answer 10

COVID
CAP
lung cancer
fungal infection
sarcoidosis

Question 11

What is Rx of TB?

Answer 11

Abx: rifampicin, izoniazid (6 months) pyrazinamid, ethambutamol (2 months)

Surgery: if MDR TB, lung resection (lobectomy or wedge resection) may be indicated

Question 12

What are complications of TB>

Answer 12

resistance

transmission

ARDS

pneumothorax

empyema

sepsis

death