POLH and xeroderma pigmentosum: XP is genetically heterogeneous with nine complementation groups associated with biallelic mutations in nucleotide excision repair (NER) genes or in the deoxyribonucleic acid (DNA) bypass polymerase POLH. In several studies, XP complementation group C (XPC) is the major disease-causing gene with a recurrent mutation in the Mediterranean region [5, 6].