Hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) or extrinsic allergic alveolitis (EAA) is a rare immune system disorder that affects the lungs. It is an inflammation of the airspaces (alveoli) and small airways (bronchioles) within the lung, caused by hypersensitivity to inhaled organic dusts and molds. [Source: Wikipedia ]

Extrinsic allergic alveolitis
Organic dust disease
OrphaNet reference
Hypersensitivity pneumonitis 
May Cause
Acute diffuse fine reticular lung opacities
Acute disseminated airspace opacity
Centrilobular small lung nodules
Chronic Kerley lines
Diffuse interstitial lung disease with associated lymphadenopathy
Diffuse mixed airspace-interstitial lung disease
Ground-glass pulmonary opacity
Ill-defined multifocal lung opacities
Interstitial lung fibrosis
Lower lung disease
Lung disease with eosinophilia
Mediastinal and/or hilar lymph node enlargement
Miliary lung opacities
Peribronchovascular interstitial thickening
Pulmonary edema
Recurrent pneumonia
Small lung nodules
Widespread small irregular lung opacities
May Be Caused by
Air-conditioner lung
Auto-worker lung
Basement shower extrinsic allergic alveolitis
Bird-fancier lung
Black fat tobacco disease
Budgerigar lung
Building-associated extrinsic allergic alveolitis
Castor bean lung
Cave explorer lung
Cheese brusher lung
Coffee-worker lung
Detergent-worker lung
Farmer lung
Fish meal-worker lung
Furrier lung
Green coffee-worker disease
Hemp dust inhalation disease
Hot-tub lung
Humidifier lung
Isocyanate-associated extrinsic allergic alveolitis
Japanese summer-type extrinsic allergic alveolitis
Machine operator lung
Malt worker pneumonia
Maple bark stripper disease
Mushroom-worker lung
Organophosphate insecticide inhalation
Ostrich feather lung
Paprika splitter lung
Pigeon-breeder lung
Pituitary snuff-taker lung
Prawn-worker lung
Starch sprayer lung
Thatched roof dust disease
Wheat weevil disease
Wood pulp-worker lung
Extrinsic allergic alveolitis
Organic dust disease