Health Encyclopedia

Hypersensitivity pneumonitis

Definition

Hypersensitivity pneumonitis is inflammation of the lungs due to breathing in a foreign substance, usually certain types of dust, fungus, or molds.

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

Hypersensitivity pneumonitis usually occurs in those who work in places where there are high levels of organic dusts, fungus, or molds. For example, farmer's lung is the most common type of hypersensitivity pneumonitis. Repeated or intense exposure to dust from moldy hay, straw, and grain can lead to lung inflammation and acute lung disease. Over time, this acute condition may turn into long-lasting (chronic) lung disease.

The condition may also result from fungus present in humidifiers, heating systems, and air conditioners found in homes and offices. Exposure to certain bird droppings (for example, among bird owners) can also lead to hypersensitivity pneumonitis.

Symptoms

Symptoms of acute hypersensitivity pneumonitis may occur 4 - 6 hours after you have left the area where the foreign substance is found. These symptoms may include:

Cough
Fever
Chills
Shortness of breath
Malaise (feeling ill)

Symptoms of chronic hypersensitivity pneumonitis may include:

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

Signs and tests

Your doctor may hear abnormal lung sounds called crackles (rales) when listening to your chest with a stethoscope.

Lung changes due to chronic hypersensitivity pneumonitis may be seen on chest x-ray. Other tests may include:

Pulmonary function tests
CBC
Hypersensitivity pneumonitis antibody panels
Aspergillus precipitins test
High-resolution CT scan of the chest
Bronchoscopy with washings and biopsy
Video-assisted or open-lung biopsy

Treatment

First, the foreign substance must be identified. Treatment involves avoiding this substance in the future. Some people may need to change jobs if they can not avoid the substance at work.

If you have a chronic form of this disease, your doctor will give you glucocorticoids (power anti-inflammatory medicines).

Expectations (prognosis)

Most symptoms go away when you avoid or limit your exposure to the material that caused the problem.

Complications

The chronic form of this disease may lead to pulmonary fibrosis (a scarring of the lung tissue that is often not reversible).

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 the material that causes the lung inflammation.

References

Hoppin JA, Umbach DM, Kullman GJ, et al. Pesticides and other Agricultural Factors Associated with Self-reported Farmer's lung among Farm Residents in the Agricultural Health Study. Occup Environ Med. 2006 Dec 20;[Epub ahead of print].

Lacasse Y, Cormier Y. Hypersensitivity pneumonitis. Orphanet J Rare Dis. 2006 Jul 3;1:25.

Review Date:3/16/2007
Reviewed By:David A. Kaufman, M.D., Assistant Professor, Division of Pulmonary, Critical Care & Sleep Medicine, Mount Sinai School of Medicine, New York, NY. Review provided by VeriMed Healthcare Network.

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