alpha 1-Antitrypsin inhibits various proteases and excessive proteolysis. If serum and tissue concentrations of this compound are low throughout longer periods of time due to deficient synthesis, - which is a dominantly inherited trait, - progressive pulmonary emphysema will develop in adults, and liver disease in more than 50% of the cases in infancy and early childhood. Three subtypes can be distinguished: the heaptitis type, the intrahepatic hypoplasia of the bile duct system, and the cholangitic type which may imitate atresia of bile ducts. Prognosis of the liver disease depends upon the time, at which inflammatory processes stop, excessive proteolysis coming to a stop at the same time. No treatment is known for this disease.