To date, the ERCC5 mutations reported result in either XP-G or in a combined XP/Cockayne syndrome (XP/CS) phenotype (Ichihashi et al., 1985; Nouspikel and Clarkson, 1994; Nouspikel et al., 1997; Okinaka et al., 1997; Zafeiriou et al., 2001; Emmert et al., 2002; Lalle et al., 2002; Moriwaki et al., 2012; Soltys et al., 2013; Fassihi et al., 2016; Zhang et al., 2017; Zhou et al., 2017). This evidence concerns the gene ERCC5 and Cowden syndrome 1.