Definition of Alpha-1 antitrypsin deficiency:

Alpha-1 antitrypsin (AAT) deficiency is a condition in which the body does not make enough of a protein that protects the lungs and liver from damage. The condition can lead to emphysema and liver disease.

Causes, incidence, and risk factors:

Alpha-1 antitrypsin (AAT) is a type of protein called a "protease inhibitor." It is made in the liver and it works to protect the lungs and liver.

AAT deficiency means there is not enough of this protein in the body. It is caused by a genetic defect. The condition is most common among Europeans and North Americans of European descent.

Studies show that AAT deficiency may be more common than was once thought.

Adults with severe deficiency will develop emphysema, often before age 40. Smoking can increase the risk of emphysema. Other patients can have higher levels of AAT in their blood, and therefore have a less severe condition.

Persons with this deficiency may also develop liver disease.