alpha 1-antitrypsin (alpha 1-AT) is a glycoprotein called an acute phase reactant, which increases in blood in a variety of inflammations. alpha 1-AT deficiency with an inherited remarkable reduction of alpha 1-AT in blood has two major disorders, pulmonary emphysema and liver diseases, particularly an infantile cirrhosis. It is of great interest that each disorder has peculiar mechanisms based on an imbalance between proteases and protease inhibitors. alpha 1-AT constitutes genetic polymorphism of which alpha 1-AT deficiency presents rare PiZ or PiZ-like variants. alpha 1-AT deficiency is an inherited metabolic disorder associated with not only a severe reduction of alpha 1-AT in blood, but also amino acid substitutions of alpha 1-AT due to gene variations.