The proteins coded by the BRCA1/2 genes, i.e., BRCA1 and 2, have a wide range of biological functions, including transcription regulation, DNA repair, etc. It has been shown that individuals carrying BRCA1 and BRCA2 mutations have ~2.2- and ~3.5-fold, respectively, higher risk of developing PC [98,99,100]. Here, BRCA1 is linked to pachyonychia congenita.