Causes of Hypersensitivity Pneumonitis

examples of hypersensitivity pneumonitis (extrinsic allergic alveolitis).

Farmer’s lung is the prototypic example of a hypersensitivity pneumonitis. There are a wide variety of other hypersensitivity pneumonitides; some of the many other causes are listed in the belwo table.

These disorders represent an allergic lung reaction to various organic dusts that can initially manifest as capillary leak pulmonary edema, but chronically result in granulomatous interstitial fibrosis. In most cases, the offending antigens are microorganisms that grow within decaying vegetable matter.

Antigens from these organisms are delivered to the lung via inhalation of dust or aerosolized contaminated water.

Notable exceptions to this general concept are bird-related hypersensitivity pneumonitides. In bird fancier’s lung, hypersensitivity occurs against bird-related antigens, such as those found in bird feathers.

Causes of Hypersensitivity Pneumonitis

EXPOSURESCAUSES
OccupationalOrganic dust
Farmer’s lungHay
Baker’s lungFlour
Sugar cane worker’s lungSugar cane dust
Cotton worker’s lungCotton dust
Mushroom worker’s lungMushrooms
Hobbies
Bird fancier’s lungBird feathers
Other exposures
Down pillows and comfortersBird feathers
Hot tubsAerosolized water
HumidifiersAerosolized water