TB

Question 1

What is tuberculosis?

Answer 1

Infectious disease of respiratory tract

Question 2

How does mycobacterium tuberculosis spread?

Answer 2

Airborne

Question 3

Describe the pathogenesis of TB (5)

Answer 3

1. Alveolar macrophages ingest bacilli. Bacilli multiply in several macrophages.
2. Neutrophil chemoattractants and cytokines released.
3. Results in inflammatory cell infiltrate reaching lung and draining hilar lymph nodes.
4. Macrophages present antigen to T lymphocytes, development of cellular immune response
5. Delayed hypersensitivity reaction occurs: result os tissue necrosis and granuloma.

Question 4

What are the general clinical features of TB? (3)

Answer 4

1. Weight loss
2. Malaise
3. Night sweats

Question 5

What are the Respiratory clinical features of TB? (4)

Answer 5

1. Cough
2. Heamoptysis
3. Breathlessness
4. Upper respiratory zone crackles

Subacute disease of gradual onset

Question 6

What are some other specific clinical features that you might see? (5)

Answer 6

1. Meningeal- headache, drowsy
2. GI- pain, periotonitis
3. Lymphadenopathy
4. Spinal- paraplegia, pain
5. Renal- failure

Question 7

Why is the Ziehl-Neeson test useful for TB?

Answer 7

Detects mycobacterium (shows up as pink stain in blue area)

Question 8

What other microbiology test can be used? why is it especially useful?

Answer 8

PCR. Can not only confirm TB but also show if its resistant to Rifampicin

Question 9

What are the distinctive histological features of TB? (2)

Answer 9

1. Mutlinucleate giant cell granulomas

2. Caseating (cheesy) Necrosis

Question 10

What are the key radiological features of TB?

Answer 10

1. Upper lobe dominance
2. Cavity formation
3. Tissue destruction
4. Scarring & shrinkage
5. Calcification

Question 11

What is miliary TB?

Answer 11

Heamatogenous spread of bacilli to multiple sites.

Question 12

What does Miliary TB look like on CXR?

Answer 12

Little nodular infiltrates throughout the lungs

Question 13

What is the initial therapy for TB?

Answer 13

1. Rifampicin
2. Isoniazid
3. Pyrazinamide
4. Ethambutol

All 4 drugs for two months?

Question 14

What is the continual therapy for TB after the 1st two months?

Answer 14

1. Rifampicin

2. Isoniazid

Question 15

What is the main side effect of Rifampicin?

Answer 15

Colours urine and all body fluids orange. Liver dysfunction

Question 16

What is the main side effect of ethambutol?

Answer 16

Optic neuritis. Liver dysfunction

Question 17

What happens in reactivation latent TB?

Answer 17

Do not develop TB during initial exposure, get it later on

Question 18

What are the features of latent TB?

Answer 18

Symptom free

Culture -

Question 19

What other infection is closely related to TB?

Answer 19

HIV

Question 20

What is a Ghon focus on a CXR?

Answer 20

Lung shadow + hilar lymphadenopathy

Question 21

What are 3 things important for Ghon focus?

Answer 21

1. Caseous Granuloma
2. lymphadenitis
3. Lymphadenopathy

Question 22

What are some tests for identifying past TB exposure?

Answer 22

1. Interferon gamma release assay- Blood sample tests for Mycobacterium antigen
2. Mantoux (skin test)- protein Tuberculin used to detect TB. cannot distinguish different types

Question 23

Why is BCG vaccination helpful?

Answer 23

BCG- weakened form of MTb