CYP2A6 and Norrie disease: Numerous studies using approaches such as genome-wide linkage, candidate gene association, and genome-wide association (GWAS) analysis have greatly advanced our knowledge of the genetic architecture underlying ND.12 The most replicated susceptibility loci for ND are nAChR subunit genes in the CHRNA5/A3/B4 cluster on chromosome 15,12–24CHRNB3/A6 on chromosome 8,12,25 and CYP2A6/A7 on chromosome 19.12,14,25 In addition, a significant association has been reported of variants in the CHRNA5/A3/B4 cluster with ND and lung cancer.18