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). The gene discussed is TWIST1; the disease is Saethre-Chotzen syndrome.