Tuberculosis

Question 1

Define tuberculosis.

Answer 1

Granulomatous disease, caused by Mycobacterium tuberculosis (aerobic).

Question 2

In which regions of the world is TB common?

Answer 2

Asia, Africa, S. America

Question 3

Name 6 risk factors for TB infection.

Answer 3

• HIV infected
• Immunocompromised e.g. HIV
• IVDA
• Smoker
• Alcohol abuse
• Homeless

Question 4

Outline the pathophysiology of primary TB infection.

Answer 4

• Inhalation of droplets, the TB in enulfed by alvolar macrophages, proliferates
• 3 weeks later, cell-mediated immunity leads to formation of granuloma with caseous centre, this contains the TB and stops it from spreading
• May also have caseous granuloma on hilar lymph nodes
• Tissue undergoes fibrosis and calcification

Question 5

What is miliary TB?

Answer 5

• When the latent TB is reactivated, it may spread to the upper lobes of the lungs
• This will lead to the formation of more caseous granulomas, and these will form cavities
• These cavities spread through the vascular system and disseminate to other organs

Question 6

What is post-primary TB?

Answer 6

When latent TB (contained in the walls of the granuloma) is reactivated

Question 7

What are some symptoms of primary TB?

Answer 7

Many are asymptomatic

Symptoms include cough, fever, malaise, erythema nodosum

Question 8

What are some symptoms of post-primary TB?

Answer 8

Fever, night sweats, weight loss, cough, haemoptysis, dyspnoea, pleuritic plain, pleural effusion

Question 9

Name some effects of miliary TB on the kidneys, brain, spinal cord, liver, endocrine system, and lymph nodes.

Answer 9

KIDNEY - sterile pyuria
BRAIN - meningitis
SPINAL CORD - Pott’s disease, cord compression
ENDOCRINE - Addison’s disease
LYMPH NODES - cervical lymphadenitis aka scrofula

Question 10

What is the key histological feature of TB?

Answer 10

Caseous granuloma

Question 11

What is the progression of disease in TB?

Answer 11

Primary –> Post-primary –> Miliary

Question 12

What investigations would you do in TB?

Answer 12

BLOODS
FBC: leukocytosis, ↓Hb

CXR

• Primary infection: peripheral consolidation and hilar lymphadenopathy.
• Post-primary infection: Upper lobe shadowing, fibrosis, calcification and cavities, pleural effusion.
• Miliary TB: Fine shadowing resembling ‘millet seeds’

SPUTUM/BRONCHIAL LAVAGE

• Culture
• Acid-Fast Bacilli (AFB) test on Ziehl-Nielsen stain - shows up as bright red

MANTOUX TEST (aka tuberculin skin test)
intradermal injxn of PPD, causes induration and erythema in 72h. If strongly positive, this indicates an active infection

HEAF TEST
Similar to Mantoux, used for grading. 3-7 days

Question 13

How would you manage TB?

Answer 13

DOT (directly observed therapy).

Should have several different antibiotics (RIPE), due to MDR – give streptomycin for highly resistant organisms.

 RIFAMPICIN
 ISONIAZID
 PYRAZINAMIDE
 ETHAMBUTOL

Consider steroids if there is pericardial or meningeal TB.

Question 14

What are the main side effects of RIFAMPICIN?

Answer 14

• Raised LFTs stop if raised bilirubin.

- Low WCC

Question 15

What are the main side effects of ISONIAZID?

Answer 15

• Raised LFTs
• Low platelets
• Stop if neuropathy

Question 16

What are the main side effects of PYRAZINAMIDE?

Answer 16

• Hepatitis
• Arthralgia
• Gout

Question 17

What are the main side effects of ETHAMBUTOL?

Answer 17

Optic neuropathy (check colour vision)

Question 18

What are some complications of primary TB?

Answer 18

Lobar collapse
Bronchiectasis
Pleural effusion

Question 19

What are some complications of post-primary TB?

Answer 19

Pleural effusion + empyema
Aspergilloma
Adenocarcinoma
Haemoptysis
Laryngeal disease