Emphysema

A disease in which the walls of the air sacs in the lungs, known as alveoli (see alveolus, pulmonary), are progessively destroyed, thus reducing the area of lung available for exchange of gases. Emphysema usually develops along with chronic bronchitis, in a condition known as chronic obstructive pulmonary disease. In almost all cases, emphysema is due to smoking. Rarely, an inherited deficiency of a chemical known as alpha-antitrypsin results in tissue damage, particularly in the lungs and liver. As the disease progresses, damage to the alveoli causes increasing shortness of breath. Once the damage to the lungs has occurred, there is no treatment that can reverse it. Stopping smoking will reduce the rate at which the lungs deteriorate.