Extrinsic allergic alveolitis & industrial dust diseases (jobs & hobbies)

Question 1

What is extrinsic allergic alveolitis (EAA)?

Answer 1

Inhalation of allergens (fungal spores or avian proteins) provokes type 3 hypersensitivity reaction.

Acutely; acute inflammatory cells

Chronically; granuloma form & obliterative bronchiolitis occur

Question 2

What are some examples and causes of EAA?

Answer 2

• Bird-fancier’s & pigeon-fancier’s lung (proteins in bird dropping)
• Farmer’s & mushroom worker’s lung
• Malt worker’s lung
• Bagassosis (cotton fibres)

Question 3

What are the clinical features of EAA?

Answer 3

4-6hr post exposure;

• Dyspnoea, fever & cough

Chronic;

• Increasing dyspnoea, type 1 resp failure
  
  • Pulmonary fibrosis
  • Granulomas & honeycomb

Question 4

What investigations would you perform for EAA?

Answer 4

Acute;

• Bloods
  
  • FBC for neutrophilia
  • Inc ESR
  • Positive serum precipitins (indicates exposure)
• CXR
  
  • Upper-zone mottling & consolidation
• Lung function tests
  
  • ​Reversible restrictive defect, reduced gas transfer during acute attack

Chronic;

• Bloods
  
  • Positive serum precipitins
• CXR
  
  • Upper-zone fibrosis & honeycomb lung
• Lung function tests
  
  • ​Persistent changes
• Bronchoalveolar lavage (BAL) fluid shows Inc lymphocytes & mast cells