It has established the diagnosis in seven typical CS cases (patients # 1 to 7) with pathogenic mutations in either ERCC6(CSB) or ERCC8(CSA), and in four XP cases (patients # 10 to 13) with mutations in POLH. The technique is also reliable in cases with uncommon phenotypes (combined features or unusually mild symptoms or very rarely involved genes). Here, POLH is linked to xeroderma pigmentosum.