Genetic disorders resulting from mutations in the ERCC5 gene, such as xeroderma pigmentosum (XP), Cockayne syndrome (CS), and tri-chothiodystrophy (TTD), underscore the biological importance of this gene [14], and most of these syndromes follow a recessive genetic model, in which heterozygotes are unaffected, but mutant homozygotes manifest the disease [27]. Here, ERCC5 is linked to Cowden syndrome 1.