extrinsic allergic alveolitis

Question 1

definition of extrinsic allergic alveolitis

Answer 1

Interstitial inflammatory disease of the distal gas-exchanging parts of the lung caused by inhalation of organic dusts.

Also known as hypersensitivity pneumonitis.

Question 2

aetiology of extrinsic allergic alveolitis

Answer 2

Inhalation of antigenic organic dusts containing microbes (bacteria, fungi or amoebae) or animal proteins = hypersensitivity response (type 3 ag-ab complex hypersensitivity reaction and type 4 granulomatous lymphocytic inflammation) in susceptible individuals

in acute phase - alveoli are infiltrated with acute inflammatory cells

with chronic exposure - granuloma formation and obliterative bronchiolitis can occur

Question 3

types of extrinsic allergic alveolitis

Answer 3

farmer’s lung

pigeon/ budgerigar fancier’s lung

Mushroom worker’s lung

Humidifier lung:

Maltworker’s lung

Bagassosis or sugar worker’s lung

Question 4

farmer’s lung

Answer 4

Mouldy hay containing thermophilic actinomycetes.

(Micropolyspora faeni, Thermoactinomyces vulgaris).

Question 5

Pigeon/budgerigar fancier’s lung

Answer 5

Bloom on bird feathers and excreta.

Question 6

Mushroom worker’s lung

Answer 6

Compost containing thermophilic actinomycetes

Question 7

Humidifier lung

Answer 7

Water-containing bacteria and Naegleria (amoeba).

Question 8

Maltworker’s lung

Answer 8

Barley or maltings containing Aspergillus clavatus.

Question 9

Bagassosis or sugar worker’s lung

Answer 9

Thermoactinomyces sacchari

Question 10

epidemiology of extrinsic allergic alveolitis

Answer 10

uncommon

2% of occupational lung diseases

50% of reported cases affect farm workers

incidence 4-10 in 100/100000/yr

marked geographical variation - dependence of occ causes

Question 11

acute sx of extrinsic allergic alveolitis

Answer 11

• presents 4-12hr post exposure
• reversible episodes
• dry cough
• dyspnoea
• malaise
• fever
• rigors
• myalgia
• wheeze and productive cough on repeat high level exposures

Question 12

chronic sx of extrinsic allergic alveolitis

Answer 12

poorly reversible manifestation in some

slowly increased breathlessness and reduced exercise tolerance

weight loss

exposure is usually chronic, low level - may be no history of acute episodes

Question 13

acute signs of extrinsic allergic alveolitis

Answer 13

rapid shallow breathing

pyrexia

inspiratory bibasal crepitations

Question 14

chronic signs of extrinsic allergic alveolitis

Answer 14

Fine inspiratory crepitations

finger clubbing - rare

type 1 resp failure

cor pulmonale

Question 15

Ix for extrinsic allergic alveolitis

Answer 15

blood

serology

CXR

high resolution CT thorax

pul func tests

bronchoalveolar lavage

Question 16

blood and serology for extrinsic allergic alveolitis

Answer 16

FBC (neutrophilia, lymphopenia)

high ESR

ABG - low ox and co2

serology: precipitating IgG to fungal or avian ag in serum - not diagnostic, often found in asymptomatic people

Question 17

cxr for extrinsic allergic alveolitis

Answer 17

normal in acute episodes

• upper zone mottling/consolidation
• hilar lymphadenopathy - rare
• may show ‘ground glass’ appearance with alveolar shadowing or nodular opacities in middle and lower zones

chronic

• fibrosis is prominent in the upper zones
• honeycomb lung

Question 18

high resolution CT for extrinsic allergic alveolitis

Answer 18

detects early changes before CXR

patchy ground glass shadowing and nodules

extensive fibrosis

Question 19

pul func tests for extrinsic allergic alveolitis

Answer 19

restrictive ventilatory defect (low FEV1, low FVC with preserved or increased ratio)

low TLCO

reduced gas transfer in acute attacks

Question 20

bronchiolar lavage for extrinsic allergic alveolitis

Answer 20

increased cellularity with high CD8+ suppressor T cells - increased lymphcytes and mast cells

lung biopsy (transbronchial or thorascopic)

Question 21

mx of hypersensitivity pneumonitis

Answer 21

avoidance
smoking cessation
pulmonary rehab
oxygen
steroids PO

Question 22

complications of hypersensitivity pneumonitis

Answer 22

• progressive deterioration in lung function
• hypoxaemia
• death