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Tuberculosis Flashcards

1
Q

What causes TB

A

mycobacterium tuberculosis

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2
Q

What is primary tb?

A

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

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3
Q

What is a ghon complex?

A

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

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4
Q

what is a ghon focus composed of?

A

tubercle-laden macrophages

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5
Q

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

A

initial lesion usual heals by fibrosis

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6
Q

What usually happens to ghon focus in immunocompromised?

A

may develop disseminated disease - military tb

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7
Q

What is secondary tb

A

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

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8
Q

What are causes of being immunocompromised and getting secondary tb?

A

immunosuppressive drugs - steroids
HIV
malnutrition

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9
Q

Where does reactivation usually occur in secondary tb?

A

apex of the lungs

can then spread locally or to more distant sites

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10
Q

what is the most common site for secondary tb?

A

lungs

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11
Q

Where may extra-pulmonary infection occur?

A 
CNS - tuberculous meningitis
Vertebral bodies - Potts disease
Cervical LN - scrofula
renal - sterile pyuria 
GI tract
hepatitis
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12
Q

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

A

Mantoux test

interferon-gamma blood test

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13
Q

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

A

induration of >15mm

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14
Q

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

A

6-15mm

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15
Q

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

A

that there is no significant hypersensitivity to the tuberculin protein

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16
Q

What may cause a false negative Mantoux test?

A 
military TB
sarcoidosis
HIV
lymphoma 
young age <6m
17
Q

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

A

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

18
Q

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

A

A positive test w a prev BCG vaccination

19
Q

What is the difference between tb infection and diseasE?

A

infection - latent, not contagious and not sick

disease - active, immune system overcome by TB

20
Q

What are RF for developing active TB

A 
silicosis
chronic renal failure
HIV
organ transplant w immunosuppression
IV drug use
haematological malignnayc
anti-tnf treatment
21
Q

explain the histological changes in tb when a lung lesion forms

A

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

22
Q

How is a diagnosis of TB made?

A

Sputum sample - x3 acid fast bacilli

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

23
Q

What are symptoms of TB w pulmonary involvement

A

persistent productive cough
breathlessness
haemoptysis

24
Q

What are symptoms of systemic TB?

A 
general:
weight loss
fever
night sweats
anorexia
malaise
25
Q

What sx suggest extra pulmonary involvement?

A 
lymphadenopathy
bone, joint, back pain 
abdo pelvic pain constipaiton 
sterile pyuria 
Headache vomiting irritability confusion 
Skin lesions - erythema nodosum
26
Q

wHAT ARE sx in children of systemic TB

A

Faltering growth
reduced energy
persistent fever

27
Q

What is the standard therapy for active TB?

A 
Initial phase (2m):
1.	Rifampicin
2.	Isoniazid
3.	Pyrazinamide
4.	Ethambutol
Then continuation phase:
- Rifampicin
- Isoniazid
28
Q

What is the treatment for latent tb?

A 
For 3m:
1.	Rifampicin
2.	Isoniazid
3.	Pyridoxine
OR
For 6m:
1.	Isoniazid
2.	Pyridoxine
29
Q

What is the treatment for meningeal TB?

A

Treat for at least 12m w addition of steroids

30
Q

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

A

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

31
Q

what are SE of rifampicin?

A

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

32
Q

What are SE of isoniazid

A

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

33
Q

What are SE of pyrazinamide?

A

hyperuricaemia -> gout
arthralgia
hepatitis

34
Q

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

A

optic neuritis - check visual acuity

35
Q

How does TB appear on Ziehl-Neelsen stain?

A

bright red

36
Q

Where do ghon complexes usually occur?

A

in the lower lobes of the lungs

37
Q

How does a ghon complex appear on XR?

A

as calcification known as a ranke complex

38
Q

Why do bacteria spread to upper lobes in secondary infection?

A

greatest area of oxygenation and the bacteria are strict aerobes

GP (10 decks)

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