Health A-Z

Medical Content Created by the Faculty of the Harvard Medical School


What Is It?

Emphysema is a respiratory disease. In this condition, millions of the lungs' tiny air sacs (alveoli) stretch out of shape or rupture. As these thin, fragile air sacs become damaged or destroyed, the lungs lose their natural elasticity. They become unable to empty easily.

Emphysema is a progressive disease, which means it continues to get worse. As the condition progresses, the lungs lose their ability to absorb oxygen and release carbon dioxide. Breathing becomes more difficult. A person feels easily short of breath, like he or she is not getting enough air.

Emphysema and chronic bronchitis are the two most common forms of chronic obstructive pulmonary disease (COPD). They often occur together. Bronchitis is an inflammation and swelling of the bronchial walls. A person with chronic bronchitis typically has a daily cough with phlegm that lasts for months at a time over several years.

Both emphysema and chronic bronchitis are caused by damage to the lungs and bronchial tubes. When the damage is caused by smoking, symptoms may improve after a smoker quits.

Smoking is responsible for the vast majority of cases of emphysema. Exposure to secondhand smoke and airborne toxins also can contribute to emphysema, though to a much lesser degree. Smokers exposed to high levels of air pollution appear to be at higher risk of developing COPD.

A small number of people in the United States develop emphysema from an inherited disease known as alpha 1-antitrypsin deficiency. In this genetic condition, the body doesn't make enough of a protein called alpha 1-antitrypsin (AAT). AAT protects the lungs from damage by enzymes. When levels of AAT are low, the lungs are prone to being damaged by these enzymes. Smoking makes this condition worse.

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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