Extrinsic Allergic Alveolitis

Question 1

Define Extrinsic Allergic Alveolitis?

Answer 1

Interstital Inflammatory disease of the distal gas-exchanging parts of the lung caused by inhalation of organic dusts
Also known as hypersensitivity pneumonitis

Question 2

What is the aetiology of Extrinsic Allergic Alveolitis?

Answer 2

Inhalation of antigenic dusts induce a hypersensitivity response in susceptible individuals
Antigenic dusts include microbes and animal proteins

Question 3

What are some examples of some conditions that can cause Extrinsic Allergic Alveolitis?

Answer 3

Farmer’s Lung
Pigeno Fancier’s Lung
Maltworker’s Lung

Question 4

What is Farmer’s Lung caused by?

Answer 4

Mouldy hay containing thermophiliic actinomycetes

Question 5

What is Pigeon Fancier’s Lung caused by?

Answer 5

Caused by blood of bird feathers and excreta

Question 6

What is Maltworker’s Lung caused by?

Answer 6

Barley or maltings containing Aspergillus clavatus

Question 7

What is the epidemiology of Extrinsic Allergic Alveolitis?

Answer 7

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

Question 8

When do the symptoms of Extrinsic Allergic Alveolitis normally present?

Answer 8

4-12 hrs after exposure

Question 9

What are the other acute symptoms of Extrinsic Allergic Alveolitis?

Answer 9

Dry cough
Dyspnoea 
Malaise 
Fever 
Myalgia

Question 10

What are the chronic symptoms of Extrinsic Allergic Alveolitis?

Answer 10

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

Question 11

What do we normally ask in a history for Extrinsic Allergic Alveolitis?

Answer 11

Full Occupational History

Enquire about hobbies and pets

Question 12

What are the acute signs of Extrinsic Allergic Alveolitis?

Answer 12

Rapid shallow breathing
Pyrexia
Inspiratory crepitations

Question 13

What are the chronic signs of Extrinsic Allergic Alveolitis?

Answer 13

Fine inspiratory crepitations

Clubbing (rare)

Question 14

What bloods do we do for Extrinsic Allergic Alveolitis?

Answer 14

FBC

ABG

Question 15

What do we see specifically on a FBC for Extrinsic Allergic Alveolitis?

Answer 15

Neutrophilia

Lymphopenia

Question 16

What do we see specificslly on an ABG for Extrinsic Allergic Alveolitis?

Answer 16

Reduced PO2 + PCO2

Question 17

What Serology test do we do for Extrinsic Allergic Alveolitis?

Answer 17

Test for IgG to fungal or avian antigens

These are not diagnostic because you may find these in normal individuals

Question 18

What do we see on a CXR for Extrinsic Allergic Alveolitis?

Answer 18

Often normal in acute episodes

Fibrosis seen in chronic cases

Question 19

What do we see on a High-Resolution CT-Thorax for Extrinsic Allergic Alveolitis?

Answer 19

Detects early changes

May show patchy ‘ground glass’ shadowing and nodules

Question 20

What do we see on Pulmonary Function Tests for Extrinsic Allergic Alveolitis?

Answer 20

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

Question 21

Whayt do we see on a Bronchoalveolar Lavage for Extrinsic Allergic Alveolitis?

Answer 21

Increased cellularity

Lung biopsy can aslo be performed