Interstitial Lung Disease

Hypersensitivity Pneumonitis

Signs and Symptoms
Diagnosis
Treatment

Signs and Symptoms

Hypersensitivity pneumonitis (HP) is an interstitial lung disease caused by repeated inhalation of certain fungal, bacterial, animal protein or reactive chemical particles, called antigens. While most people who breathe in these antigens don't develop problems, in some people, the body's immune reaction to these particles causes inflammation of the lung. In some cases, parts of the lungs may become scarred.

It's not known why a minority of people exposed to these antigens develop HP. Their genetics and environment may interact to make them more susceptible to the disease.

HP should not be confused with the more common types of allergies, which are caused by small amounts of proteins in the environment such as dust mites, cat dander, pollen and grass. Having seasonal or environmental allergies has nothing to do with having or developing HP.

Hypersensitivity pneumonitis (HP) is subdivided into two forms: acute and chronic. Symptoms differ for each form.

• The acute form of HP occurs after heavy, often short-term exposure to the antigen. Symptoms appear relatively suddenly and include fever, chills, fatigue, breathlessness, chest tightness and cough. If the person is removed from the antigen exposure, the symptoms usually resolve over 24 to 48 hours. Recovery is often complete.



• The chronic form of HP is thought to occur due to longer term, low-level exposure to the antigen, and it often causes more subtle symptoms. Patients with chronic HP often describe chronic symptoms, such as shortness of breath or cough, that have gotten worse. Symptoms may worsen at work, at home or wherever the patient is being exposed to the antigen, but most often, patients with chronic HP haven't had acute episodes. Most patients seen in our clinic have the chronic form of HP.

Reviewed by health care specialists at UCSF Medical Center.
Last updated June 11, 2009