Definition:

Alpha-1-antitrypsin (A1AT) deficiency is a genetic disorder characterized by low plasma levels of A1AT. The condition is associated with emphysematous lung disease and also with liver disease. A1AT is the archetype of the serine protease inhibitor. Mutations in the A1AT gene lead to misfolding of the protein and accumulation within the endoplasmic reticulum of hepatocytes. The accumulation of mutant A1AT protein has a directly toxic effect on the liver, resulting in hepatitis and cirrhosis. And the decrease in circulating A1AT results in protease-antiprotease imbalance at the lung surface and emphysema ensues.