Hypersensitivity pneumonitis / extrinsic allergic alveolitis

Question 1

What is hypersensitivity pneumonitis?

Answer 1

Inhalation of allergens (fungal spores or avian proteins) provokes a hypersensitivity reaction

Question 2

What is the most common type?

Answer 2

Farmer’s lung

Question 3

Describe the acute phase?

Answer 3

alveoli are infiltrated with acute inflammatory cells

Question 4

Describe the chronic phase?

Answer 4

granuloma formation and obliterative bronchiolitis occurs

Question 5

What are clinical features of acute exposure?

Answer 5

Fever 
Cough 
SOB 
Malaise
Myalgia 
Rigors 
On examination- tachypnoea and coarse end inspiratory crackles and wheezes.

Question 6

What are clinical features of chronic exposure?

Answer 6

Weight loss
Cough 
Exertional dyspnoea and increasing dyspnoea
Type 1 respiratory failure 
Cor pulmonale

Question 7

Farmer’s lung is associated with forking mouldy hay and vegetable material, what organisms are responsible?

Answer 7

Micropolyspora faeni,

Thermoactinomyces vulgaris

Question 8

What other causes of hypersensitivity pneumonitis are there?

Answer 8

Bird fanciers lung 
Cheese washers lung
Wine makers lung
Mushroom worker
Humidifier fever 
Malt workers lung

Question 9

What will a chest Xray show?

Answer 9

Acute: consolidation,
Chronic: upper zone fibrosis and honey comb lung

Question 10

What will FBC show?

Answer 10

raised WBCs in acute cases, raised ESR, ABGs and positive serum precipitins

Question 11

What will lung function tests show?

Answer 11

Lung function shows restrictive defect and decrease in gas transfer (Tco)

Question 12

What does broncholavage show?

Answer 12

Bronchoalveolarlavage shows increased T cells and granulocytes.

Question 13

What is treatment for acute cases?

Answer 13

Remove allergen, give O2

Oral prednisolone

Question 14

What is treatment for chronic cases?

Answer 14

Avoid exposure to antigen
Long term Prednisolone in large doses may cause regression of the disease.
Compensation may be payable