Moreover, because non-syndromic sagittal and metopic craniosynostosis comprise half of all craniosynostoses (Slater et al., 2008; Greenwood et al., 2014), SMAD6/BMP2 genotypes are inferred to account for ~3.5% of all craniosynostosis, and are likely rivaled in frequency only by mutations in FGFR2 as the most frequent cause of all craniosynostoses (Twigg and Wilkie, 2015). This evidence concerns the gene FGFR2 and craniosynostosis.