There are eleven genes (CCND1, FN1, CTNNB1, CASP3, RHOA, FGF2, CXCL8, STAT1, MMP9, NRAS, and MET) that were not only significantly up-regulated in PC but also obviously related to poor prognosis of PC (Fig. 4a-f and Supplementary Figure 4A–E), and selected for candidate hub genes. Here, MMP9 is linked to pachyonychia congenita.