CYP2C9 and chronic obstructive pulmonary disease: That is, 56% of the top 100 genes, 66% of the top 50 genes and 90% of the top 10 genes were associated with COPD in literature, such as CYP2E1 (Rank: 1), CYP2C9 (Rank: 4), NOS1 (Rank: 5) and CYP1B1 (Rank: 8).