Hypersensitivity pneumonitis (extrinsic allergic alveolitis)

Hypersensitivity pneumonitis is a condition where the lungs become infalmmed due to exposure to an environmental allergen to which the individual has ben previously sensitized.



  • dyspnea
  • cough

The disease may be of chronic nature with symptoms lasting more than a year (Lynch et al, 1995). The disease may be chronic and progressive. In some cases the disease may progress to end stage lung disease where the lung can no longer supply tissues with sufficient oxygen to meet the body’s metabolic needs (Ando et al, 2003).


confirmed through the following

  • demonstration of interstitial markings on chest radiographs
  • serum precipitating antibodies against offending antigens
  • a lymphocytic alveolitis on bronchoalveolar lavage (BAL), and/or a granulomatous reaction on lung biopsies.
Type Specific antigen Exposure
Bird-Breeder’s Lung
Also called Bird fancier’s lung,
Pigeon-Breeder’s Lung, and Poultry-Worker’s Lung.
Avian proteins Feathers and bird droppings [2]
Farmer’s Lung The molds

Generally from moldy hay[2] but may be found elsewhere.
Bagassosis Thermophilic actinomycetes[2] Moldy bagasse (pressed sugarcane).
Malt Worker’s Lung Aspergillus clavatus[2] Moldy barley.
Maple bark disease Cryptostroma corticale[2] Moldy maple bark
Miller’s lung Sitophilus granarius (wheat weevil)[2] Dust-contaminated grain[2]
Humidifier Lung The bacterias

  • T. candidus
  • Bacillus subtilis
  • B. cereus, and Klebsiella oxytoca;
  • Thermophilic actinomycetes[2]

the fungus

and the amoebae

  • Naegleria gruberi,
  • Acanthamoeba polyhaga, and
  • Acanthamoeba castellani.
Mist generated by a machine from standing water.
Mushroom Worker’s Lung Thermophilic actinomycetes Exposure is from mushroom compost.
Compost Lung Aspergillus compost.
Peat Moss Worker’s Lung Caused by Monocillium sp. and Penicillium citreonigrum Peat moss.
Suberosis Penicillum frequentans Moldy cork dust.
Japanese Summer-Type HP Trichosporon cutaneum Damp wood and mats.
Cheese-Washer’s Lung Pencillum casei[2] or P.roqueforti Cheese casings.
Metalworking Fluids HP Nontuberculous Mycobacteria. Mist from metalworking fluids.
Hot Tub Lung Mycobacterium avium complex Mist from hot tubs.
Mollusc Shell HP Aquatic animal proteins Mollusc shell dust.
Isocyanate HP TDI, HDI, and MDI Paints, resins, and polyurethane foams.
chemical worker’s lung[2]
Trimellitic anhydride[2] Plastics, resins, and paints.
Berylliosis Beryllium Electronics industry.
Wine-grower’s lung Botrytis cinerea mold Moldy grapes
Lifeguard Lung Aerosolized Endotoxin Prolonged exposure to poor ventilation in an indoor aquatic facility




Treating hypersensitivity pneumonitis (HP) involves both identifying and removing the antigen that’s causing the condition, and taking anti-inflammatory medication.

Removing the Antigen: If the inhaled antigen can be recognized and removed, the lung inflammation in acute HP is often reversible.


Lynch, DA, Newell, JD, Logan, PM, King Jr, TE and Muller NL. 1995. Can CT distinguish hypersensitivity pneumonitis from idiopathic pulmonary fibrosis? American Journal of Roentgenology. 165: 807-811. 

Ando, Masayuki, Colby, Thomas V , Cormier, Yvon, Costabel, Ulrich, Dalphin, Jean-Charles, Erkinjuntti-Pekkanen, Riitta, Lacasse, Yves, Morell, Ferran, Müller, Selman, Moises , Schuyler, Mark. 2003. Clinical Diagnosis of Hypersensitivity Pneumonitis. American Journal of Respiratory and Critical Care Medicine. 168: 952-958.


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