ARHGAP1 and pachyonychia congenita: On the other side, among multiple factors implicated in the initiation and progression of PC (Xu et al. 2002; Albany et al. 2011; Hsieh et al. 2001) tumor suppressor gene DLC1, a member of RhoGAP family of genes, stands out, as it has been shown to be down-regulated or absent not only in PC, but in various other solid tumors and hematological malignancies (Guan et al. 2006; Durkin et al. 2007; Ullmannova et al. 2009).