Notably, mutations in the XPB (MIM 133510), XPD (MIM 126340) and GTF2H5 (encoding the p8/TTDA protein, (MIM 608780)) genes are mainly associated with rare autosomal recessive disorders such as Xeroderma pigmentosum (XP), the combination of XP with Cockayne syndrome (XP/CS), and Trichothiodystrophy (TTD). Here, GTF2H5 is linked to Cowden syndrome 1.