Alpha-1 Antitrypsin deficiency (AAT deficiency) is an inherited condition that may cause lung and liver disease. Alpha-1 antitrypsin (AAT) is a protein that is made in the liver and protects the lungs. If the AAT proteins aren't the right shape, they get stuck in the liver cells and are unable to reach the lungs. Some people have AAT Deficiency no symptoms at all and do not develop additional complications. Performing simple blood tests and looking at genetic tests can determine if you have Alpha-1 Antitrypsin deficiency. If tests indicate that your lungs are affected, your doctor may also want to have additional testing done.