Tuberculosis (RESP)

Question 1

Define TB.

Answer 1

An infectious, chronic, granulomatous disease

Question 2

Which organism is TB caused by?

Answer 2

Mycobacterium tuberculosis

Question 3

What body parts does TB affect?

Answer 3

Typically lungs (pulmonary TB) especially upper lobes, but can spread to any organ haematologically to cause extrapulmonary TB

Question 4

Describe the disease progression from primary to secondary TB.

Answer 4

• Mycobacterium tuberculosis is dormant in many patients before it progresses to active TB
• primary TB is asymptomatic and occurs in immunocompetent individuals who are exposed to M. tuberculosis - this usually heals
• (initial infection may be pulmonary or rarely GI and is typically lower lobe initially)
• if host becomes immunocompromised, the initial infection may become reactivated into secondary TB
• miliary TB occurs if there is haematogenous dissemination of TB

Question 5

What does accumulation of lymphocytes and macrophages cause in TB?

Answer 5

Accumulation of lymphocytes and macrophages in the initial phase –> formation of caseating granulomas (associated with necrosis) in the lungs and other organs –> develop latency

Question 6

What is miliary TB?

Answer 6

Potentially fatal form of TB resulting from haematogenous dissemination of TB:

• kidneys causing sterile pyuria
• meningitis
• lumbar vertebrae –> Pott disease
• adrenals causing Addison’s
• liver causing hepatitis
• cervical lymph nodes

Question 7

What are some risk factors for TB? (7)

Answer 7

• exposure to infection
• immunosuppression (diabetes, Cushing’s, steroid use)
• silicosis (form of lung fibrosis)
• HIV
• malignancy
• birth in an endemic country (India, Bangladesh, Sub-Saharan Africa)
• overcrowded areas

Question 8

What are some examples of immunosuppression that increase TB risk? (3)

Answer 8

• diabetes
• Cushing’s
• steroid use
• (HIV)

Question 9

Birth in which endemic countries increase TB risk? (3)

Answer 9

• India
• Bangladesh
• Sub-Saharan Africa

Question 10

What are the clinical features of TB? (10)

Answer 10

• cough - productive (may have haemoptysis) + does not respond to conventional Abx therapy
• fever (chronic, fluctuating)
• weight loss
• night sweats
• SOB
• anorexia
• malaise
• pleuritic chest pain
• cervical lymphadenopathy + hilar lymphadenopathy
• Pott’s disease –> spread to bones

Question 11

What are some clinical features of miliary TB? (4)

Answer 11

• fever
• weight loss
• meningitis
• yellow caseous tubercles spread to other organisms

Question 12

What might you see on examination in TB? (6)

Answer 12

• chest exam may be normal in mild-moderate disease
• crackles
• bronchial breath sounds
• amphoric breath sounds (distant hollow breath sounds heard over cavities)
• clubbing (chronic disease)
• erythema nodosum, erythema induratum

Question 13

What is the 1st-line investigation for TB?

Answer 13

Chest X-ray

Question 14

What can CXR show for TB? (4)

Answer 14

• caseating granulomas - cavitating lesion in upper lobe
• consolidation / fibronodular opacities (in upper lobes usually) with or without cavitation
• bilateral hilar lymphadenopathy
• pleural effusion

Question 15

What is the gold-standard diagnostic test for TB?

Answer 15

Sputum culture - most sensitive and specific test

Question 16

What is a sputum acid-fast bacilli smear for TB?

Answer 16

• uses a Ziehl-Neelson stain or auramine stain
• acid fast bacillus +ve in TB

Question 17

What test for another disease is offered to TB patients?

Answer 17

HIV test

Question 18

What test is usually offered for contacts of infected TB patients and what does it screen for?

Answer 18

Mantoux test - screens for latent TB

(Purified protein derivative - PPD is injected intradermally, erythema occurs after 72h)

Question 19

What can cause a false negative on the Mantoux test for latent TB? (4)

Answer 19

Immunosuppression:

• sarcoidosis
• steroid use
• lymphoma
• AIDS
• (age extremes, fever, hypoalbuminuria, anaemia)

Question 20

What might FBC show in TB?

Answer 20

• leukocytosis
• anaemia seen in 10%

Question 21

What is seen on histology in TB?

Answer 21

Caseating granulomas

Question 22

What are some differential diagnoses for TB? (6)

Answer 22

• COVID-19
• community acquired pneumonia
• lung cancer
• non-tuberculous mycobacteria
• fungal infection
• sarcoidosis

Question 23

What is the 1st line management for latent TB? (2)

Answer 23

• 3 months of isoniazid (with pyridoxine) and rifampicin
• OR 6 months of isoniazid (with pyridoxine)

Question 24

What is the 1st line management for active TB? (4)

Answer 24

RIPE

• Rifampicin - 6 months
• Isoniazid - 6 months
• Pyrazinamide - 2 months
• Ethambutol - 2 months

Question 25

How do we manage meningeal TB?

Answer 25

RIPE for prolonged period (at least 12 months) + steroids

Question 26

What is a side effect of rifampicin (TB)?

Answer 26

Red/orange secretions - tears, urine

Question 27

What are some side effects of isoniazid (TB)? (2)

Answer 27

- drug-induced lupus - peripheral neuropathy - give pyridoxine (vitamin B6) to prevent - e.g. pellagra (vitamin B3 deficiency) --> triad of dementia, diarrhoea and dermatitis --> death if untreated - e.g. sideroblastic anaemia

Question 28

What is a side effect of pyrazinamide (TB)?

Answer 28

Can cause gout due to hyperuricaemia

Question 29

What is a side effect of ethambutol (TB)?

Answer 29

May cause optic neuritis (colour blindness, loss of visual acuity, and restriction of visual fields)

Question 30

How do we manage meningeal TB?

Answer 30

RIPE for at least 12 months + steroids

Question 31

What is a complication of TB treatment?

Answer 31

- immune reconstitution disease - occurs typically 3-6 weeks after starting treatment - often presents with enlarging lymph nodes

Question 32

What needs to be done before giving BCG vaccine for TB?

Answer 32

Tuberculin skin test to check for past exposure to TB

Question 33

What is MDR-TB? | Multi drug resistant TB

Answer 33

TB that is resistant to 2+ first-line drugs including rifampicin and isoniazid - risk factors: - previous drug treatment for TB - incorrect dosages - non-adherence - travel to endemic regions - social risk factors (alcohol, drugs, homeless, prison) - exposure to patient with MDR-TB - HIV seropositivity

Question 34

What are some complications of TB? (7)

Answer 34

- transmission of TB - immune reconstitution inflammatory syndrome - ARDS - pneumothorax - haemoptysis - bronchiectasis - empyema

Question 35

What is the mortality rate for TB without treatment?

Answer 35

>50%

Question 36

What is the prognosis like for treated TB?

Answer 36

In general, patients can expect to do well with minimal or no sequelae