Tuberculosis

Question 1

What causes TB

Answer 1

mycobacterium tuberculosis

Question 2

What is primary tb?

Answer 2

when a non-immune host who is exposed develops primary infection in the lung

Question 3

What is a ghon complex?

Answer 3

combination of a ghon focus (lung lesion) and lymph node

Question 4

what is a ghon focus composed of?

Answer 4

tubercle-laden macrophages

Question 5

What is the usual natural history of primary TB in immunocompetent?

Answer 5

initial lesion usual heals by fibrosis

Question 6

What usually happens to ghon focus in immunocompromised?

Answer 6

may develop disseminated disease - military tb

Question 7

What is secondary tb

Answer 7

a host who has had the infection before (either asymptomatically or had it and recovered) becomes immunocompromised and the initial inf is reactivated

Question 8

What are causes of being immunocompromised and getting secondary tb?

Answer 8

immunosuppressive drugs - steroids
HIV
malnutrition

Question 9

Where does reactivation usually occur in secondary tb?

Answer 9

apex of the lungs

can then spread locally or to more distant sites

Question 10

what is the most common site for secondary tb?

Answer 10

lungs

Question 11

Where may extra-pulmonary infection occur?

Answer 11

CNS - tuberculous meningitis
Vertebral bodies - Potts disease
Cervical LN - scrofula
renal - sterile pyuria 
GI tract
hepatitis

Question 12

What is the main test for latent tb? give an alternative

Answer 12

Mantoux test

interferon-gamma blood test

Question 13

What result of the test for latent tb suggests tb infection?

Answer 13

induration of >15mm

Question 14

What result of the test for latent tb suggests previous TB infection or BCG

Answer 14

6-15mm

Question 15

What does a result of <6mm in the TB test mean?

Answer 15

that there is no significant hypersensitivity to the tuberculin protein

Question 16

What may cause a false negative Mantoux test?

Answer 16

military TB
sarcoidosis
HIV
lymphoma 
young age <6m

Question 17

When would a smaller induration be expected in the Mantoux test?

Answer 17

if they have HIV or are immunosuppressed due to reduced ability to develop a hypersensitivity response

Question 18

What is involved in the Mantoux test?What is highly suggestive of TB?

Answer 18

A positive test w a prev BCG vaccination

Question 19

What is the difference between tb infection and diseasE?

Answer 19

infection - latent, not contagious and not sick

disease - active, immune system overcome by TB

Question 20

What are RF for developing active TB

Answer 20

silicosis
chronic renal failure
HIV
organ transplant w immunosuppression
IV drug use
haematological malignnayc
anti-tnf treatment

Question 21

explain the histological changes in tb when a lung lesion forms

Answer 21

ghon focus -> granuloma (collection of epithelioid histiocytes) -> caseous necrosis in the centre

Question 22

How is a diagnosis of TB made?

Answer 22

Sputum sample - x3 acid fast bacilli

CXR - cavity, pleural effusion, lymphadenopathy, parenchymal infiltrates mainly in apexes

Question 23

What are symptoms of TB w pulmonary involvement

Answer 23

persistent productive cough
breathlessness
haemoptysis

Question 24

What are symptoms of systemic TB?

Answer 24

general:
weight loss
fever
night sweats
anorexia
malaise

Question 25

What sx suggest extra pulmonary involvement?

Answer 25

``` lymphadenopathy bone, joint, back pain abdo pelvic pain constipaiton sterile pyuria Headache vomiting irritability confusion Skin lesions - erythema nodosum ```

Question 26

wHAT ARE sx in children of systemic TB

Answer 26

Faltering growth reduced energy persistent fever

Question 27

What is the standard therapy for active TB?

Answer 27

``` Initial phase (2m): 1. Rifampicin 2. Isoniazid 3. Pyrazinamide 4. Ethambutol Then continuation phase: - Rifampicin - Isoniazid ```

Question 28

What is the treatment for latent tb?

Answer 28

``` For 3m: 1. Rifampicin 2. Isoniazid 3. Pyridoxine OR For 6m: 1. Isoniazid 2. Pyridoxine ```

Question 29

What is the treatment for meningeal TB?

Answer 29

Treat for at least 12m w addition of steroids

Question 30

What groups of people require directly observed therapy w three times a week dosing regimen?

Answer 30

homeless people with active tuberculosis patients who are likely to have poor concordance all prisoners with active or latent tuberculosis

Question 31

what are SE of rifampicin?

Answer 31

potent liver enzyme inducer hepatitis orange secretions (urine) flu like sx

Question 32

What are SE of isoniazid

Answer 32

peripheral neuropathy (prevented w pyridoxine) vit b6 hepatitis, agranulocytosis liver enzyme inhibitor

Question 33

What are SE of pyrazinamide?

Answer 33

hyperuricaemia -> gout arthralgia hepatitis

Question 34

What are SE of ethambutol? what ix does this prompt before starting and during rx?

Answer 34

optic neuritis - check visual acuity

Question 35

How does TB appear on Ziehl-Neelsen stain?

Answer 35

bright red

Question 36

Where do ghon complexes usually occur?

Answer 36

in the lower lobes of the lungs

Question 37

How does a ghon complex appear on XR?

Answer 37

as calcification known as a ranke complex

Question 38

Why do bacteria spread to upper lobes in secondary infection?

Answer 38

greatest area of oxygenation and the bacteria are strict aerobes