Indeed, since the first description of CS by Dr. Cockayne in 1936, only eleven patients have been reported in the Tunisian population: two siblings with one of the mutations described in the present study (c.598_600delinsAA) in ERCC8/CSA [14, 15], two other siblings with a private mutation (c.400-2A > G) in ERCC8/CSA [20], and three patients with the novel c3156dup mutation in ERCC6/CSB [10]. Here, ERCC8 is linked to Cowden syndrome 1.