Although both the XP-V and the heterozygous carriers display lower mutation frequency relative to the controls, the overall mutation frequency is not significantly different in all groups (Fig. 1A,B), showing in average 5.1 mutations per 100 bp for the wild-type (POLH homozygous) controls, 4.5/100 bp for the carrier (POLH heterozygous) controls, and 4.5/100 for the XP-V patients, which strikingly differs from the XP-V patients of the French cohort. The gene discussed is POLH; the disease is Xeroderma pigmentosum variant.