Radiological appearance of extrinsic allergic alveolitis

The features of extrinsic allergic alveolitis on chest radiography include:

• no abnormality in the early disease
  
  
• the lungs are small with some ground glass shadowing
  
  
• with regular exposure to the allergen:
  • fluffy, nodular or streaky shadowing develops
  • the upper lobes are more commonly affected
  • these shadows represent areas of granuloma formation and fibrosis
    
    
• in severe disease there may be areas of honeycomb lung