Pairs of a photosensitive and a non-photosensitive CS patient sharing the same homozygous mutations have been described for the less severe form (type I) for ERCC6/CSB (CS22PV/CS28PV) [2] and in our previous study for ERCC8/CSA (CS11/CS16) [23] (Supplementary Table S1). Here, ERCC6 is linked to Cowden syndrome 1.