In addition, other candidate genes may need to be considered, including GJB6 encoding connexin 30,20 desmoglein 1 (DSG1),21 desmoplakin (DSP),22 keratin 9 (KRT9),17 and frizzled 6,23,24 mutations in that mimic some features of the PC phenotype and hence should be encompassed into the differential diagnosis of PC. This evidence concerns the gene KRT9 and pachyonychia congenita.