In terms of the etiological mechanism of craniosynostosis in AS, mutation of FGFR2 at either S252W or P253R has been reported to cause loss of ligand specificity and decrease the dissociation rate of FGFs from FGFR2, resulting in activated FGF/FGFR signaling. The gene discussed is FGFR2; the disease is craniosynostosis.