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).

Support Groups

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.

Images

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.

---

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process, and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health on the Net Foundation (www.hon.ch.)

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. ©1997-2008 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.