SERPINA1 and alpha 1-antitrypsin deficiency: Inherited severe ZZ AATD is a cause of emphysema (loss of function due to a low serum AAT protein level, i.e., <20% of the normal 0.9–2 g/L) and liver diseases (gain of function due to the polymerisation and intracellular overload of AAT) (Zuo et al., 2016).