Extrinsic allergic alveolitis

Question 1

Define extrinsic allergic alveolitis

Answer 1

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

AKA hypersensitivity pneumonitis

Question 2

Aetiology of extrinsic allergic alveolitis

2

Answer 2

Inhalation of antigenic dusts induces a hypersensitivity response in susceptible individuals
Antigenic dusts include microbes & animal proteins

Question 3

Examples of extrinsic allergic alveolitis

3

Answer 3

Farmer’s lung - caused by mouldy hay containing thermophilic actinomycetes

Pigeon fancier’s lung - caused by blood on bird feathers & excreta

Maltworker’s lung - caused by barley or malting containing Aspergillus clavatus

Question 4

Epidemiology of extrinsic allergic alveolitis

prevalence, groups x3

Answer 4

UNCOMMON
2% of occupational lung disease
50% of reported cases affect farm workers
Geographical variation

Question 5

Presenting symptoms of extrinsic allergic alveolitis - acute

7

Answer 5

Present 4-12 hrs after exposure
Reversible episode of
- dry cough
- dyspnoea
- malaise
- fever
- myalgia
Wheeze & productive cough may develop if repeat high level exposure

Question 6

Presenting symptoms of extrinsic allergic alveolitis - chronic
(4)

Answer 6

Slowly increasing breathlessness
Decreased exercise tolerance
Weight loss
Exposure usually chronic, low level & may be no history of previous acute episodes

Question 7

Signs of extrinsic allergic alveolitis on physical examination - acute
(3)

Answer 7

Rapid shallow breathing
Pyrexia
Inspiratory crepitations

Question 8

Signs of extrinsic allergic alveolitis on physical examination - chronic
(2)

Answer 8

Fine inspiratory crepitations

Clubbing (rare)

Question 9

Investigations for extrinsic allergic alveolitis

6 types

Answer 9

Bloods
Serology
CXR
High resolution CT thorax
Pulmonary function tests
Bronchoalveolar lavage

Question 10

Investigations for extrinsic allergic alveolitis - bloods

2

Answer 10

FBC - neutrophilia, lymphopenia

ABG - reduced PO2 + PCO2

Question 11

Investigations for extrinsic allergic alveolitis - serology

Answer 11

Test for IgG to fungal or avian antigens (not diagnostic)

Question 12

Investigations for extrinsic allergic alveolitis - CXR

2

Answer 12

Often NORMAL in acute episodes

Fibrosis may be seen in chronic cases

Question 13

Investigations for extrinsic allergic alveolitis - high resolution CT thorax
(2)

Answer 13

Detects early changes

May show patchy “ground glass” shadowing & nodules

Question 14

Investigations for extrinsic allergic alveolitis - pulmonary function tests
(3)

Answer 14

Restrictive defect (low FEV1, low FVC)
Preserved or increased FEV1/FVC ratio
Reduced total lung capacity

Question 15

Investigations for extrinsic allergic alveolitis - bronchoalveolar lavage
(2)

Answer 15

Increased cellularity

Lung biopsy can also be performed