extrinsic allergic alveolitis

- due to inhalation of a number of different antigens, most common being microbial spores containing vegetable matter.
- delayed hypersensitivity reaction which maybe immune complex (III) or cell mediated (IV)
- eg: farmer's lung (Micropolyspora faeni), bird fancier's lung, maltworker's lung, humidifier fever
- typically fever, malaise, cough and shortness of breath several hours after exposure to antigen.
- basal crackle is a feature
- NO wheeze
- causes upper zone fibrosis
- NO eosinophilia
- positive serum precipitating antibodies (circulating IgG precipitins)
- treatment: avoidance of causative allergen and long term corticosteroid therapy