The reason that CS shows some overlaps with certain forms of xeroderma pigmentosum, a very rare skin disorder which is primarily caused by the mutation of Xeroderma pigmentosum complementation group A (XPA) and shows the most severe skin symptoms and progressive neurological disorders in some cases (Lehky et al., 2021) may be because XPA works both in GG-NER and TC-NER. The gene discussed is XPA; the disease is skin disorder.