Approximately 40% of CDC73 mutations identified in patients with sporadic PC are germline mutations (Table 5 and Figures 2 and 3), and of these CDC73 mutations ∼65% occur in exons 1, 2, and 7, and the majority are frameshift or nonsense mutations, resulting in premature protein truncation and loss of protein function (Table 5) (Marsh et al., 2007; Newey et al., 2010). This evidence concerns the gene CDC73 and pachyonychia congenita.