Tuberculosis

Question 1

Describe the global distribution of tuberculosis and its impact on tuberculosis in the UK.

Answer 1

• The disease burden from
• High prevalence countries (India, China, Indonesia, Philippines, Africa)
• 70% are non UK born, aged 15-44
• London is a risk factor (39% of TB cases in UK)

TB globally is falling.

• TB is the number one killer of communicable diseases
• TB is the leading killer of people with HIV
• Kills more than HIV and malaria together.

Question 2

Describe the histopathology of tuberculosis.

Answer 2

• Granulomatous inflammation

Question 3

at risk

Answer 3

• HIV positive, immunosuppressed

- Elderly, neonates, diabetics

Question 4

outline the pathogenesis of tuberculosis in its primary, post- primary and fibrocaseous forms in the lung.

Answer 4

• M. tuberculosis, M.africanum, M. bovis (bovine TB, BCG strain)

“Infection - inhalation of droplet nuclei.
M. tuberculosis is deposited in alveoli & engulfed by alveolar macrophages.
Proliferating bacilli kill macrophages & are released.

”

Question 5

describe mycobacteria tuberculosis.

Answer 5

• Non-motile bacillus, very slowly growing (disease is slow, the treatment is long)
• Aerobic (has a predilection for apices of lungs)
• Uniquely has a very thick fatty cell wall (Resistant to acids, alkalis and detergents
  neutrophil and macrophage destruction)

Question 6

what do Th1 cells do in response to M. Tb, and what does this cause?

Answer 6

Th1 cells & macrophages form a granuloma to prevent further growth - latent TB

-Eliminates the number of invading mycobacteria but causes tissue destruction because of the activation of macrophages

Question 7

Describe the pathogenesis of tuberculosis in its primary, post- primary form.

Answer 7

• No preceding exposure or immunity
• Progressive or latent or cleared.
• Mycobacteria is spread via lymphatics and drains to hilar lymph nodes

In the majority (>85%)
Initial lesion + local lymph node (Primary complex)
Heals with or without scar. May calcify (Ghon focus + complex)
Associated with development of immunity to tuberculoprotein

• Primary infection progresses to Tuberculous bronchopneumonia
• Primary focus continues to enlarge - cavitation
• Enlarged hilar lymph compress bronchi, lobar collapse
• Enlarged lymph node discharges into bronchus
• Poor prognosis
• In a small number (1-3%)
• Miliary TB (looked like millet seeds on autopsy) develops, with hematogenous spread of bacteria to multiple organs
• Fine mottling on X-ray, widespread small granulomata
• CNS TB in 10-30%

Question 8

hypotheses behind post-primary disease

Answer 8

• TB entering a dormant stage with low or no replication over prolonged periods of time
• Balanced state of replication and destruction by immune mechanisms

Question 9

Describe the common clinical presentations of tuberculosis.

Answer 9

Usually presents with no symptoms

• Cough
• Fever
• Sweats (mainly at night)
• Weight loss
• malaise

Question 10

Describe the public health duties of doctors managing cases of Tuberculosis.

Answer 10

• CXR should be obtained
• 3 sputum samples
• nucleic acid amplification test (NAAT) should be performed on at least one respiratory specimen.

Question 11

Define the major groups of antituberculous drugs, their pharmacological profiles and side effects, and their practical application in the management of tuberculosis.

Answer 11

• Isoniazid (H)
• Pyrazinamide (z)
• Rifampicin ( R)
• Ethambutol (E)
• R and H for the entire 6 months
• -E and z for the first two months

Question 12

side effects of isoniazid

Answer 12

• Hepatitis

- Peripheral neuropathy

Question 13

side effects of pyrazinamide

Answer 13

• hepatitis

Question 14

side effects of rifampicin

Answer 14

• orange pee

- hepatitis

Question 15

how can active tb occur

Answer 15

-progression of primary disease or reactivation of latent disease

Question 16

what a cxr would show

Answer 16

• At the apices, there is soft “fluffy” upper zone
• Cavitation in 10-30%
• Lymphadenopathy is rare

Question 17

latent tb screening

Answer 17

normal CXR

but also positive Mantoux test, IGRA