Emphysema is a long-term (chronic) lung disease. With emphysema, the tiny air sacs (alveoli) at the end of the airways in the lungs are damaged and lose their stretch. When the air sacs are damaged or destroyed, their walls break down and the sacs become larger. These larger air sacs move less oxygen into the blood. This causes problems with breathing and shortness of breath. These symptoms often get worse over time. After air sacs are destroyed, they can't be replaced.

Emphysema is often caused by smoking. A less common type of emphysema is caused by the lack of a substance in the lungs called alpha-1 antitrypsin. This type of emphysema is usually inherited.