SERPINA1 and alpha 1-antitrypsin deficiency: Because AATD-associated emphysema represents a more homogenous phenotype of COPD, with a more rapid decline in pulmonary status, generally at a younger age with fewer comorbidities, it offers a potential model for understanding COPD pathogenesis with respect to proteinases beyond those directly inhibited by alpha1-antitrypsin [2,6].