SERPINA1 and Alpha-1-antitrypsin deficiency: Alpha-1 antitrypsin deficiency (AATD) is an inherited condition characterized by reduced plasma levels of alpha-1 antitrypsin (AAT), often leading to pulmonary diseases primarily emphysema and/or chronic obstructive pulmonary disease (COPD), but also bronchiectasis, bronchial asthma, or other less common disorders.