A form of alveolitis or pneumonitis due to an acquired hypersensitivity to inhaled avian antigens, usually proteins in the dust of bird feathers and droppings.

Synonyms: Pigeon Breeder Lung, Bird Fancier's Lung, Lungs, Bird Fancier's, Budgerigar Fancier's Lungs, Budgerigar Fanciers Lung, Budgerigar Fancier Lung, Pneumonitides, Avian Hypersensitivity, Lung, Bird Fancier's, Pneumonitis, Hypersensitivity, Avian, Bird Fancier Lung, Pneumonitis, Avian Hypersensitivity, Avian Hypersensitivity Pneumonitis, Bird Fanciers Lung, Hypersensitivity Pneumonitides, Avian, Lungs, Pigeon Breeder's, Pigeon Breeders Lung, Pigeon Breeder's Lungs, Pigeon Breeder's Lung, Bird Fancier's Lungs, Lungs, Budgerigar Fancier's, Avian Hypersensitivity Pneumonitides, Lung, Budgerigar Fancier's, Hypersensitivity Pneumonitis, Avian, Budgerigar Fancier's Lung, Lung, Pigeon Breeder's