Tuberculosis

Question 1

Describe the pathogenesis of primary TB. (5)

Answer 1

1. TB enters the lungs and lodges in peripheral alveoli, causing macrophage/lymphocyte activation
2. Macrophages turn into epithelioid cells and form granulomas
3. Several granulomas aggregate to form a Ghon complex
4. Bacteria spread from the Ghon complex to the hilar lymph nodes, activating the immune response
5. Immune response causes formation of a fibrous cap around the Ghon complex; this calcifies to form the Ranke complex
   a. This is now latent TB

Question 2

Describe the pathogenesis of secondary/reactivated TB. (2)

Answer 2

1. Calcified Ranke complexes may be reactivated in the apex of the lungs
2. Active TB causes cavity formation in the lungs
   a. This destroys lung tissue
   b. Cavities open into the bronchi, which spreads TB via coughing

Question 3

List 3 factors which might reactivate TB.

Answer 3

Smoking
Immunosuppression
HIV infection

Question 4

Which bacteria causes TB?

Answer 4

Mycobacterium tuberculosis

Question 5

List 4 samples you might take to investigate TB.

Answer 5

Deep sputum sample
Bronchioalveolar lavage
Other fluid samples (for extra-pulmonary TB)
Tissue biopsy (for extra-pulmonary TB)

Question 6

List 5 microbiology tests you might do for TB.

Answer 6

Ziehl-Neelsen stain
Auramine fluorescence staining
Tuberculin skin test
Nucleic acid amplification test (NAAT)
Sample cultures

Question 7

How do you test for latent TB?

Answer 7

Mantoux test

Question 8

List 2 types of pulmonary TB.

Answer 8

Miliary TB:
-Diffuse, aggressive TB throughout the whole lung

Secondary TB:

• Indolent onset
• Systemic symptoms
• Progressive pulmonary symptoms

Question 9

Describe the symptoms of pulmonary TB. (7)

Answer 9

Flu-like symptoms
Asymptomatic
Chronic cough
Haemoptysis
Weight loss
Unexplained fever
Spontaneous pneumothorax

Question 10

Describe the signs you would find on clinical examination of TB. (7)

Answer 10

Hilar/paratracheal lymphadenopathy
Lung collapse
Consolidation
Obstructive emphysema
Cavitation
Pleural effusion (exudative)
Endobronchial vs miliaryTB

Question 11

List 6 complications of pulmonary TB.

Answer 11

Meningitis
Percarditis
Massive haemoptysis
Aspergilloma
Obstructive airway disease
Bronchopleural fistula

Question 12

List 2 common sites of extra-pulmonary TB.

List 4 less common sites of extra-pulmonary TB.

Answer 12

COMMON SITES:
CNS
Kidneys

LESS COMMON SITES:
GI tract
Pericardium
Bones and joints
Genitourinary disease

Question 13

Which 4 antibiotics are used to treat TB?

Answer 13

Pyrazinamide
Isoniazid
Rifampicin
Ethambutol

Question 14

What are the side effects of pyrazinamide? (1)

Answer 14

Liver toxicity

Question 15

What are the side effects of isoniazid? (3)

Which one can be prevented? How?

Answer 15

Neuropathy
Liver toxicity
B3 deficiency

Neuropathy/B3 deficiency can be prevented by giving pyridoxine

Question 16

What are the side effects of rifampicin? (4)

Answer 16

Red urine
Liver toxicity
Bone marrow toxicity
Kidney toxicity

Question 17

What are the side effects of ethambutol? (1)

Answer 17

Optic neuritis

Question 18

How long should TB therapy be?

Answer 18

6 months

Question 19

Describe the standard course of TB therapy. (4)

Answer 19

Start with all 4 drugs
Stop ethambutol if bacteria are sensitive to rifampicin and isoniazid
Stop pyrazinamide after 2 months
Give pyridoxine to prevent peripheral neuropathy (caused by isoniazid)