Hu et al. recently compared genomic data of 3,030 affected cases and a normal cohort, and found that 5.5% of the affected cases harbored mutation in 6 genes associated with increased PC risk (CDKN2A, TP53, MLH1, BRCA1, BRCA2, and ATM) [70]. Here, MLH1 is linked to pachyonychia congenita.