MedlinePlus Medical Encyclopedia: Hypersensitivity pneumonitis

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Hypersensitivity pneumonitis

Contents of this page:
Illustrations Alternative names Definition Causes, incidence, and risk factors Symptoms Signs and tests	Treatment Expectations (prognosis) Complications Calling your health care provider Prevention

Illustrations

Bronchoscopy

Respiratory system

Alternative names Return to top

Extrinsic allergic alveolitis; Farmer's lung; Mushroom picker's disease; Humidifier or air-conditioner lung; Bird breeder's lung

Definition Return to top

Hypersensitivity pneumonitis is 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.

Causes, incidence, and risk factors Return to top

Hypersensitivity pneumonitis is usually an occupational disease in which exposure to organic dusts, fungus, or molds leads to acute and then, over time, chronic lung disease. Exposure may also occur in the home, from fungus present in humidifiers, heating systems, and air conditioners. Some people may have hobbies that can lead to exposure, such as owning birds.

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).

Symptoms Return to top

Acute hypersensitivity pneumonitis may have the following symptoms:

Cough
Fever
Chills
Shortness of breath
Malaise (feeling ill)

Chronic hypersensitivity pneumonitis may have the following symptoms:

Breathlessness, especially with exertion
Cough, often dry
Loss of appetite
Unintentional weight loss

Signs and tests Return to top

Crackles (rales) may be heard when a stethoscope is used to examine the chest.

Tests include the following:

Chest X-ray
Pulmonary function tests
CBC
Hypersensitivity pneumonitis antibody panels
Aspergillus precipitins test
High-resolution CT scan of the chest
Bronchoscopy with washings or transtracheal biopsy

Treatment Return to top

Treatment seeks to identify the offending allergen and avoid further exposure to it. A change of occupations may be necessary if future worksite exposure is 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) Return to top

Most symptoms resolve after exposure to the allergen is limited.

Complications Return to top

Pulmonary fibrosis is a possible complication of hypersensitivity pneumonitis.

Calling your health care provider Return to top

Call your health care provider if symptoms of hypersensitivity pneumonitis develop.

Prevention Return to top

The chronic form can be prevented by avoiding further exposure after the offending substance has been identified.

Update Date: 5/7/2003

Updated by: David A. Kaufman, M.D., Pulmonary & Critical Care Medicine, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.

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