Alpha‐1 antitrypsin deficiency (AATD) is caused by loss‐of‐function mutations in SERPINA1/alpha‐1 antitrypsin mutant Z protein (ATZ), which compromises the ability of ATZ to properly fold and leads to its accumulation in the ER of hepatocytes. This evidence concerns the gene SERPINA1 and alpha 1-antitrypsin deficiency.