ZNF660 and pachyonychia congenita: For further large‐scale validation, we used 450K array data to investigate ST6GALNAC3 and ZNF660 promoter methylation levels in two independent patient sample sets (sample set 1: 21 NM vs 20 PC; sample set 2: 11 AN vs 19 PC) as well as in the publicly available TCGA RP cohort (50 AN vs 497 PC) (Table S3) (Cancer Genome Atlas Research, 2015).