Interstitial lung diseases - EXTRINSIC ALLERGIC ALVEOLITIS (HYPERSENSITIVITY PNEUMONITIS)

Question 1

What is hypersensitivity pneumonitis?

Answer 1

inflammation of the alveoli within the lung caused by hypersensitivity (an allergic reaction) to inhaled organic dust.

Question 2

what are the causes of hypersensitivity pneumonitis?

Answer 2

1) avian antigens
= brid fanciers lung

2) thermophilic actinomycetes
= farmers lung
= malt & mushroom workers

3) drugs
= gold
= bleomycin
= sulphasalazine

Question 3

how can hypersensitivity pneumonitis be classified?

Answer 3

1) acute
2) sub-acute
3) chronic

Question 4

In acute hypersensitivity pneumonitis, how many hours after exposure do symptoms occur?

Answer 4

4-6hours following exposure

Question 5

what are the symptoms of acute hypersensitivity pneumonitis?

Answer 5

• fever
• cough
• breathlessness and dyspnoea
• myalgia

Question 6

what are the signs of acute hypersensitivity pneumonitis?

Answer 6

• pyrexia (raised body temp)
• crackles
• no wheeze
• hypoxia can occur

Question 7

how long after removal from the antigen does resolution occur?

Answer 7

24-48hours

Question 8

in subacute hypersensitivity pneumonitis, how long after removal from exposure can improvement be seen?

Answer 8

weeks to months

Question 9

in what conditions will chronic hypersensitivity pneumonitis occur?

Answer 9

when there has been repeated low dose antigen exposure over time (years)

Question 10

what are the symptoms fo chronic hypersensitivity pneumonitis?

Answer 10

• cough
• breathlessness
• weight loss
• malaise

Question 11

what are the signs of chronic hypersensitivity pneumonitis?

Answer 11

• crackles

- finger clubbing may be present

Question 12

what investigation should be done in order to diagnose hypersensitivity pneumonitis?

Answer 12

1) chest X-ray
2) High resolution CT scan
3) lung function tests
4) precipitating antibodies
5) broncho-alveolar lavage
6) lung biopsy

Question 13

when hypersensitivity pneumonitis is chronic, what would a chest X-ray show?

Answer 13

• diffuse small nodules

- increased reticular shadowing

Question 14

in a high resolution CT scan, where are most abnormalities found?

Answer 14

they are found in the mid to upper zones

Question 15

what would a high resolution CT scan show?

Answer 15

it would show;

• nodules with ground glass opacity
• evidence of air trapping
• increased reticulation & honeycombing

Question 16

in lung function test what results would you expect to find?

Answer 16

• restrictive lung pattern

- decreased carbon monoxide gas transfer seen in CHRONIC DISEASE

Question 17

what information from the broncho-alveolar lavage would help you distinguish between hypersensitivity pneumonitis from sarcoidosis?

Answer 17

Hypersensitivity pneumonitis has a LOWER CD4+: CD8+ ratio

Question 18

if a lung biopsy were to be done, what cell would the infiltrate be rich in?

Answer 18

it would be lymphocyte rich

Question 19

how would you manage hypersensitivity pneumonitis?

Answer 19

1) avoidance of the allergen

2) if even with avoidance of the antigen the symptoms are still bad then steroids should be given
= PREDNISOLONE

Question 20

what is the name of the fever that is a typical feature of hypersensitivity pneumonitis?

Answer 20

HUMIDIFIER FEVER

Question 21

what causes humidifier fever ?

Answer 21

• humidifiers

- air conditions units that emit a fine spray of antigenic mciro-organisms.