An inflammation in the lungs caused by exposure to an allergen (foreign substance), usually organic dust. This dust may come from animal dander, molds, or plants.
Alternative Names
Extrinsic allergic alveolitis; Farmer's lung; Mushroom picker's disease; Humidifier or air-conditioner lung; Bird breeder's lung
Causes, incidence, and risk factors
This is usually an occupational disease in which exposure to organic dusts, fungus, or molds leads to acute and over time, chronic lung disease . Exposure may also occur in the home, from fungus (molds) present in humidifiers, heating systems, and air conditioners. Some people (for example, bird owners) may have hobbies that can lead to exposure. Acute illness may occur 4 to 6 hours after the exposure, once the person has left the area where the allergen is present. Chronic illness with changes seen on chest X-ray may develop with continued exposures. The chronic form of this disease may lead to pulmonary fibrosis (a scarring of the lung tissue that is often not reversible).
Signs and tests
Crackles (rales) may be heard when a stethoscope is used to examine the chest.
Tests include:
chest X-raypulmonary function testsCBC hypersensitivity pneumonitis antibody panels
aspergillus precipitins high-resolution CAT scan of the chest bronchoscopy with washings or transtracheal biopsy
Treatment
Treatment seeks to identify the offending allergen and avoid further exposure to it. A change of occupations may be indicated in cases where future worksite exposure would be unavoidable. In chronic forms of the disease, treatment with glucocorticoids (a type of steroid drugs) can be tried because this may decrease inflammation.
Expectations (prognosis)
Most symptoms resolve after exposure to the allergen is limited.
Calling your health care provider
Call your health care provider if symptoms of hypersensitivity pneumonitis develop.
Prevention
The chronic form can be prevented by avoiding further exposure after the offending substance has been identified.