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YR6: RESPIRATORY > Tuberculosis > Flashcards

Tuberculosis Flashcards

1
Q

What happens in primary TB?

A

1st encounter
Lung lesion “Ghon focus” develops: composed of tubercle-laden macrophages
Combination of a Ghon focus + hilar LNs = Ghon complex

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2
Q

How is TB transmitted?

A

Inhalation of respiratory droplets from infectious active pulmonary TB cough

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3
Q

What are the outcomes of primary TB infection?

A

Immediate clearance. Asymptomatic
TB contained (disease is dormant): caseating granuloma formation. Asymptomatic
Primary disease: TB disseminates due to inadequate immune response

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4
Q

What is secondary TB? What is it usually precipitated by? Where does it usually occur?

A

Reactivation of dormant TB (5-10% lifetime risk)
Precipitated by impaired immune function
Occurs in lung apices

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5
Q

List 6 risk factors for TB

A

Born in high prevalence area
Close contact with TB patient
Homeless, alcohol dependent, IVDUs
Immunosuppression
Co-morbidities
Age <5y

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6
Q

List 4 co-morbidities increasing the risk of TB

A

HIV
DM
End-stage CKD
Occupational lung disease e.g. silicosis

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7
Q

List 3 immunosuppressive drug classes increasing risk of TB

A

High dose CS
Chemotherapy
Biologics e.g. TNF alpha inhibitors- Infliximab

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8
Q

List 5 constitutional symptoms a patient with TB may complain of

A

Fever
Night sweats
Weight loss
Anorexia
Malaise

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9
Q

List 3 pulmonary symptoms that occur in TB

A

Chronic, initially dry, then productive cough; purulent sputum
Dyspnoea
Haemoptysis

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10
Q

What extra-pulmonary symptoms of TB may arise?

A

Lymphadenopathy
Bone/ joint pain
GI: Abdo pain, constipation, obstruction
GU: Dysuria, haematuria
TB meningitis: Headaches, vomiting
Cutaneous: erythema nodosum

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11
Q

What is TB?

A

Granulomatous disease caused by Mycobacterium tuberculosis

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12
Q

What are the 3 subtypes of TB?

A

Primary: initial infection; pulmonary or GI (rare)
Post-primary: Reinfection/ reactvation
Miliary: Haematogenous dissemination

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13
Q

Give 4 features of Mycobacterium Tuberculosis

A

Intracellular organism
Acid fast bacilli
Survives after being phagocytosed by macrophages
Aerobe: prefers upper lung lobes

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14
Q

List 4 signs of TB on examination

A

Fever
Clubbing
Auscultation: crackles, bronchial breath sounds or normal
Wasting

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15
Q

What initial investigations should be performed for suspected active TB?

A

3x Sputum samples for microscopy, culture + NAAT
CXR

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16
Q

What is used in microscopy for TB and what does this detect?

A

Ziehl-Neelsen stain for acid-fast bacilli

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17
Q

What is the gold standard investigation for TB? What is the issue of relying on this?

A

Sputum culture with Lowenstein-Jensen agar
Culturing TB takes a long time (~ 6w)

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18
Q

If unable to produce an adequate sputum sample, what other investigations can be used for TB?

A

Bronchoalveolar lavage sample, Pleural fluid or gastric aspirate for culture.
Pleural biopsy or lung biopsy if other testing not diagnostic.

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19
Q

What is seen on CXR in primary TB?

A

Hilar lymphadenopathy
Pleural effusion
Pulmonary infiltrates
Consolidation

20
Q

What is seen on CXR in post-primary TB?

A

Upper lobe consolidation
Fibrocaseous cavitary lesions in upper lobes
Calcification

21
Q

What is the treatment for active TB?

A

Rifampicin (6 months)
Isonizid (6 months) + Pyridoxine (Via B6)
Pyrazinamide (2 months)
Ethambutol (2 months)

22
Q

In which patients is directly observed therapy indicated with a 3x a week dosing regimen?

A

Homeless + active TB
Patients who are likely to have poor concordance
Prisoner with active or latent TB

23
Q

What is the treatment for latent TB?

A

Rifampicin + Isoniazid for 3 months
OR
Isoniazid (+ pyridoxine) for 6 months

24
Q

How does treatment for patients with meningeal TB differ?

A

Treated for prolonged period >,12 months with the addition of steroids

25
Q

What is extra pulmonary TB? In which patients does this most commonly occur?

A

TB involving organs other than the lungs

Immunocomprimised

26
Q

What lymph, dermatological, CVS and adrenal signs and symptoms may arise from caseous tubercles spreading in miliary TB?

A

Lymphadenopathy
Skin: lupus vulgaris
Heart: pericardial effusion, constrictive pericarditis
Adrenals: Addisons

27
Q

When are IGRAs useful? What occurs?

A

Useful in latent TB (high specificity)
Negative in BCG vaccine
Exposure of host T cells to TB antigens leads to release of interferon

28
Q

Why is IGRA testing preferred to TSTs?

A

Single patient visit

BCG does NOT give false positive

29
Q

What are the 2 forms of testing for TB?

A

Tuberculin Tests: Mantoux test +Heaf Test

Interferon Gamma Tests (IGRA)

30
Q

How should cultures be taken in suspected TB?

A

Sputum acid-fast bacilli smear (3 samples 8h apart, with 1 being in early morning)

31
Q

What is shown by tuberculin skin tests?

A

Positive if previous exposure to TB or BCG

Negative TST doesn’t rule out TB

32
Q

What is the Mantoux test? What does it identify?

A

Erythema after 72h of PPD injection suggests patient has previously been exposed to TB.
Identifies those exposed to TB
DOES NOT distinguish between active + latent TB.

33
Q

What is the Heaf test? How is it interpreted?

A

PPD on forearm. Graded according to papule size + vesiculation
(ring-shaped induration)

34
Q

What is the limitation of the IGRA test?

A

Does not differentiate between latent + active TB

35
Q

What is a Ghon focus?

A

Granuloma in which central tissue has died due to caseous necrosis
Sequela of primary TB infection

36
Q

What is a Ghon complex comprised of? What may this progress to if calcified?

A

Ghon focus + ipsilateral mediastinal lymphadenopathy
Ranke complex

37
Q

What is a Ranke complex?

A

a Ghon lesion that has undergone calcification
+
an ipsilateral calcified mediastinal node

38
Q

Which anti-TB antibiotic is an enzyme inducer? Thus what drugs need to be considered?

A

Rifampicin
OCP

39
Q

Give 3 side effects of Rifampicin

A

Orange / red secretions
CYP450 induction
Raised transaminases

40
Q

Give 2 side effects of Isoniazid

A

Peripheral neuropathy (B6 deficiency)
Hepatotoxicity

41
Q

Give 2 side effects of Pyrazinamide

A

Hyperuricaemia
Hepatotoxicity

42
Q

Give a side effect of Ethambutol

A

Optic neuritis
(Pain, vision loss, 1 eye)

43
Q

MOA of Rifampicin

A

inhibits RNA polymerase

44
Q

MOA of Isoniazid

A

Decreased mycolic acid synthesis (part of cell wall)

45
Q

MOA of Pyrazinamide

A

Unknown

46
Q

MOA of Ethambutol

A

Decreased polymerisation of cell wall

YR6: RESPIRATORY (38 decks)

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