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Respiratory System > Tuberculosis > Flashcards

Tuberculosis Flashcards

1
Q

TB stats

A
  • No. 1 communicable disease, causes more death than HIV + malaria combined
  • 2 times more common in women
  • 2 billion people infected world-wide
  • 15 times more likely to get TB if non-UK born
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2
Q

which 8 countries have 2/3 of TB cases?

A

India, China, Indonesia, Philippines, Nigeria, Bangladesh, South Africa

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3
Q

vulnerable groups for TB

A
  • elderly, neonates
  • immunocompromised, HIV
  • from high-prevalent countries
  • age 15-44
  • diabetic
  • underlying nutritional state
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4
Q

3 TB - causing organisms

A
  1. M. tuberculosis
  2. M. africanum
  3. M. bovis
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5
Q

non TB organisms

A
  • atypical mycobacteria infections

- M. leprea

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6
Q

describe MTB (mycobacterium tuberculosis)

A
  • slow growing (therefore takes a long time before strain and treatment is determined)
  • thick walled (resistant to macrophages, neutrophils, acids, alkalines, detergent, alcohol)
  • non-motile
  • require long treatment courses
  • aerobic (therefore TB is mostly found at the apices of the lungs where there V>Q and there is less gas exchange)
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7
Q

transmission of TB

A
  • airborne
  • only pulmonary and laryngeal TB communicable, but TB can affect may organs
  • requires prolonged exposure
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8
Q

progression of inflammatory response in TB

A

activated macrophages –>

  1. –> cytokine response –> T cells (kills the pathogens)
  2. –> epitheloid cells –> Languan’s giant cells –> granuloma formation
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9
Q

what type of infection is TB?

A

IL-6 mediated pyogenic infection

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10
Q

3 possible outcomes of primary TB infection

A
  1. progressive disease
  2. contained latent
  3. cleared and cured (lung can heal with or without scar)
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11
Q

describe primary TB infection and its common presentations

A
  • no preceding exposure
  • MTB spread through the lymphatics to the draining hilar lymph nodes
  • usually no symptoms aside from: fever, malaise, possible chest signs
  • erythema nodosum
  • Gohn focus (past TB)
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12
Q

complications of primary TB infection

A
  • severe bronchial pneumonia (1%)

- miliary TB (1-3%)

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13
Q

describe severe bronchial pneumonia as complication of TB

A
  • cavitation: the primary focus continues to enlarge
  • enlarged hilar lymph node compresses the bronchi –> lobar collapse
  • enlarged lymph node discharges into the bronchus
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14
Q

describe miliary TB

A
  • shows as millet seeds in autopsy
  • caused by spread of TB from blood to lungs
  • in 10-30%, there is haematogenous spread (by blood) to CNS TB, the rest to other organs
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15
Q

describe post primary TB and 2 reasons why it can go unnoticed

A
  • the kind of TB that we see the most.
  • only in humans, animals die from primary TB
  • take decades to develop, therefore the person probs have TB from childhood.
  • 85% of cases will heal on its own

why it goes unnoticed until now:

  1. MTB enters latent stage and does not proliferate
  2. there is equal proliferation of MTB and destruction by immune cells
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16
Q

timeline for TB disease progression

A

primary complex –> progressive primary disease –> miliary TB, meningeal TB, pleural TB (after 6-12 months) –> post primary disease (pulmonaryTB, skeletal TB ) (after 1-5 years) –> genitourinary TB, cutaneous TB (after 10-15 years)

17
Q

TB presentation

A
  • fever (absent in 37%)
  • weightloss (absent in 38%)
  • night sweats (absent in 39%)
  • all 3 absent in 25%
  • cough (only in pulmonaryTB - about half of all TB)
  • fluffy nodular upper zone cavitation in 10-30%
  • CRP (normal in 15%)
  • ESR (erthrocyte sedimentation rate) - normal in 21%
18
Q

investigations for TB:

A
  • CXR (sometimes will show as normal)
  • CT
  • lymphadenopathy
  • CRP
  • ESR
  • BAL
  • sputum samples (8-24 hours apart, one morning sample)
  • lumbar puncture in CNS TB
  • urine test in urogenital TB
  • biopsy, tissue sample
  • Manoux or IGRA
19
Q

when to consider C scan for TB

A
  • normal CXR but suspect miliary TB
  • cavitation or other differential
  • lymphadenopathy present (enlarged lymph nodes)
  • when planning to conduct bronchoalveolar lavage/washing (BAL)
20
Q

alternative diagnosis for TB

A
  • granulomas/ giant cells present
  • lymphadenopathy (pneumonia does not have this, but some other conditions do, make sure to eliminate those first) - usually unilateral, 15% bilateral
21
Q

describe BAL

A

bronchoscope passed into the lungs through nose/mouth. Water is squirted into a part of the lungs and collected for analysis

22
Q

5 drugs for TB and the year they were discovered

A
  1. streptomycin - 1944 (not used anymore, resistance)
  2. isoniazide (H) - 1952
  3. pyrazinamide (Z) - 1952
  4. rifampicin (R) - 1957
  5. ethambutol (E) - 1961
23
Q

standard treatment plan for TB

A

2 months of 4 drugs (R/H/Z/E) + 4 months of 2 drugs (R/H)

total of 6 months, around 12 tablets per day

24
Q

alternate TB treatment plans

A
  • 7-9 months monoresistance treatment (single-agent?)
  • 12 months (for CNS TB, H monoresistance extensive disease)
  • 9-12-18-20 months (MDR-RR TB)
25
Q

other TB drugs

A
  • pyridoxine (vit B6) + isoniazid - reduces neuropathy
  • steroids (for CNS, miliary, pericardial TB)
  • vit D substitution
  • BCG vaccination (in UK only given to children at risk)
26
Q

effectiveness of drugs?

A
  • 99% MTB dead in 2 days upon using isoniazid

- 99% MTB dead in 14 days upon using rifampicin

27
Q

side effects of rifampicin

A
  • orange urine
  • induces liver enzymes
  • all hormonal contraceptives ineffective
  • hepatitis
28
Q

side effects of isoniazide

A
  • hepatitis

- peripheral neuropathy (pyridoxine vit B6)

29
Q

side effects of pyrazinamide

A
  • hepatitis

- gout

30
Q

side effects if ethambutol

A

-optic neuropathy

31
Q

eligibility for screening for latent TB

A
  • aged < 65 and in contact with people with active TB
  • recently came from high risk areas
  • inhibited TNF-alpha
  • positive reaction of TB tests
32
Q

treatment for LATENT TB

A
  • H/R for 3 months
  • H for 6 months
  • R for 6 months
  • H/R once weekly for 12 weeks for those who are non-compliant (unlikely to take full course of medicine)
33
Q

3 things that indicate it is TB

A
  1. Langhans giant cells in histology
  2. raised CRP - Ilb-mediated response to infection
  3. raised erythrocyte sedimentation rate (ESR) - inflammation

Respiratory System (13 decks)

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