Alpha-1 Antitrypsin Deficiency (Alpha-1) is a condition that is passed from parents to their children through their genes.  This condition may result in serious lung and/or liver disease at various ages in life.   For each trait a person inherits, there are usually two genes and one gene comes from each parent. People with Alpha-1 have received two defective alpha-1 antitrypsin genes. One defective gene came from their mother and one from their father. There are many types of defective alpha-1 antitrypsin genes. The most common abnormal genes are called S and Z. Normal genes are called M. A person who does not have Alpha-1 will have two M genes (MM). People identified with Alpha-1 most commonly have two Z genes (ZZ). Current evidence suggests that about 100,000 people with Alpha-1 (ZZ) in the United States. Another deficient gene combination is SZ, although people with this gene combination are less likely to get lung or liver problems than those with two Z genes.

Alpha-1 occurs when there is a lack of a protein in the blood called alpha-1 antitrypsin or AAT that is produced by the liver. The main function of AAT is to protect the lungs from inflammation caused by infection and inhaled irritants such as tobacco smoke. The low level of AAT in the blood occurs because the AAT is abnormal and cannot be released from the liver at the normal rate. This leads to a build up of abnormal AAT in the liver that can cause liver disease and a decrease of AAT in the blood that can lead to lung disease.