SERPINA1 and pulmonary emphysema: In fact, people with inherited AAT deficiency (AATD) have reduced levels of circulating AAT, which is strongly linked to an increased risk of developing early-onset pulmonary emphysema (Laurell and Eriksson, 1963; Hutchison, 1973), a pathology, at least in part, characterized by the protease-antiprotease imbalance.