FGFR1 and Saethre-Chotzen syndrome: However, genetic factors have a determinant role in the etiology of SCS, and there are several known core genes (FGFR1, FGFR2, FGFR3, TWIST1) associated with classical CS syndromes, such as Crouzon, Saethre–Chotzen, Pfeiffer, Muenke, and Apert (Muenke et al., 1994; Reardon et al., 1994; Wilkie et al., 1995; Bellus et al., 1996; Howard et al., 1997).