Extrinsic Allergic Alveolitis

Question 1

What type of hypersensitivity reaction causes EAA?

Answer 1

Type III Hypersensitivity

Question 2

Which immune cells cause alveolitis in EAA?

Answer 2

Lymphocytes

Question 3

What is another name for EAA?

Answer 3

Hypersensitivity pneumonitis

Question 4

What are the different types of EAA?

Answer 4

Bird/Pigeon fancier’s lung
Farmer’s/Mushroom WOrker’s lung
Drugs - gold, bleomycin, sulphasalazine

Question 5

What causes Bird fancier’s lung?

Answer 5

Protein in bird droppings

Question 6

What causes farmer’s / mushroom worker’s lung?

Answer 6

Micropolyspora fauna

Thermoactinomyces sacchari

Question 7

What is acute extrinsic allergic alveolitis?

Answer 7

Alveoli infiltration by acute inflammatory cells

Question 8

What is chronic extrinsic allergic alveolitis?

Answer 8

Granuloma, obliterative bronchiolitis can occur

Question 9

How does acute EAA present?

Answer 9

Fevers
Rigors
Myalgia
Dry cough 
Dyspnoea 
Crackles (but no wheeze) 
Hypoxia

Question 10

What are signs of chronic EAA?

Answer 10

Progressive breathlessness
Weight loss 
Exertion-induced dyspnoea 
Type 1 respiratory failure 
Cor pulmonale

Question 11

When do the symptoms of EAA start after antigen exposure?

Answer 11

Several hours after acute exposure (flu-like)

Question 12

What might be seen on the CXR of someone with acute EAA?

Answer 12

Upper zone mottling / consolidation

Hilar lymphadenopathy

Question 13

What would the pulmonary function test show for EAA?

Answer 13

Restrictive patten

low FEV1 and FVC, normal ratio, low gas transfer

Question 14

How is acute EAA diagnosed?

Answer 14

FBC
ESR increased
ABGs
Positive serum precipitins 
CXR

Question 15

What might be seen on the CXR of someone with chronic EAA?

Answer 15

Pulmonary fibrosis

Question 16

How do you treat acute EAA?

Answer 16

Remove allergen
Give O2 (35-60%)
Oral prednisolone (40 mg/24 hr PO followed by reducing dose)

Question 17

What causes chronic EAA?

Answer 17

Repeated antigen exposure

Question 18

How do you diagnose chronic EAA?

Answer 18

Hx of exposure
Positive serum precipitins
Lung biopsy if doubt
BAL shows increased lymphocytes and mast cells

Question 19

How do you treat chronic EAA?

Answer 19

Avoid exposure to allergens or wear face mask or positive pressure helmet
Long-term steroids often achieve CXR+physiological improvements