Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Emphysema

What Is It?

Emphysema is a respiratory disease in which 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 and are unable to empty easily. Emphysema is a progressive disease, which means it continues to get worse. As the condition progresses, the lungs also lose their ability to absorb oxygen and release carbon dioxide. Breathing becomes more difficult, and 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), and they often occur together. A person with chronic bronchitis (an inflammation and swelling of the bronchial walls) 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, and this damage is usually permanent. When the damage is caused by smoking, symptoms may improve after a smoker quits.

Smoking is responsible for up to 90% of cases of emphysema. Exposure to secondhand smoke and airborne toxins also can contribute to emphysema, although these factors are much less important than smoking. Smokers exposed to high levels of air pollution, including sulfur dioxide and particulates, appear to be at higher risk of developing COPD.

About 1% 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), which protects the lungs from damage by enzymes. When levels of AAT are low, the lungs are prone to being damaged by these enzymes. In its most severe form, emphysema can develop in people in their 30s or 40s. Because smoking interferes with the function of AAT, people with AAT deficiency who smoke develop more severe emphysema at an earlier age than those who don't smoke. Most people with AAT deficiency are Caucasians of northern European descent.

COPD is the most common cause of death from respiratory disease in the United States. Most people with emphysema are cigarette-smoking men older than age 40, who live in areas where pollution is a constant problem. However, because of the dramatic increase in smoking among women over the past few decades, the rate of emphysema in women continues to climb.