Hypersensitivity Pneumonitis (EAA)

Question 1

What is hypersensitivity pneumonitis?

Answer 1

A sensitised indivual breathes in allergens resulting in type 3/4 hypersensitivity reaction

Question 2

How does EAA occur acutely?

Answer 2

Allergen causes acute inflammation in the alveoli and interstitium:
Fever - Chills - Malaise - Dyspnoea - Cough - Crackles - Tachypnoea

Question 3

How does EAA occur chronically?

Answer 3

Chronic exposure leads to chronic inflammation, granuloma formation and fibrosis
Insidious Cough
Progressive dyspnoea (often noticed first as exertional)
Weight loss
Malaise
Crackles
Wheeze

Eventually Type 1 resp failure and Cor Pulmonale

Question 4

What tests can be done in an acute instance of hypersensitivity pneumonitis?

Answer 4

FBC - neutrophilia from reaction to allergen + antibody levels
ESR + CRP - increased erythrocte sedimentation rate
ABGs
PFTs - reversible restrictive pattern and lower gas transfer
+ve Serum Precipitans (antibodies)
CXR - Upper zone mottling/consolidation

Question 5

What investigations are availble for chronic HP?

Answer 5

CXR - Mostly upper zone fibrosis and honeycomb lung
PFT - Irreversible restrictive pattern and reduced gas transfer
+ve serum precipitans (antibodies)
Bronchoalveolar Lavage

Question 6

How is HP treated?

Answer 6

Allergen avoidance
O2 acutely and in severe chronic LTOT
Oral Prednisalone acutely
Prednisalone may be used long term to improve physiological and CXR.

Question 7

NAme some varieties of hypersensitivity pneumonitis?

Answer 7

Bird Fanciers Lung/Pigeon fanciers Lung (proteins in feathers and bird droppings)
Farmers & mushroom workers lung
Malt Workers Lung (aspergillus Clavatus)
Sugar Workers Lung