In addition, the mutant protease inhibitor (Pi) Z homozygote of the SERPINA1 gene, which can increase individual susceptibility to COPD, is rare across worldwide populations (0.001% – 4.5%), especially in Asians (< 0.004%), and accountable for only 2% COPD patients [9]. This evidence concerns the gene SERPINA1 and chronic obstructive pulmonary disease.