Three of the genome-wide significant loci have known associations with ND from our prior GWAS and others6: chr15q2521–23 (smallest P = 1.6 × 10−39 for rs16969968, a well-established functional missense [D398N] CHRNA5 SNP24) chr20q1321 (smallest P = 1.2 × 10−12 for rs151176846, an intronic CHRNA4 SNP), and chr9q3422 (smallest P = 1.1 × 10−8 for rs13284520, an intronic DBH SNP). This evidence concerns the gene CHRNA4 and Norrie disease.