Gain-of-function mutations in fibroblast growth factor receptor 1 (FGFR1), FGFR2 and FGFR3 are responsible for many craniosynostosis syndromes, including bent bone dysplasia and Crouzon, Apert, Pfieffer, Beare–Stevenson and Muenke syndromes, among others. The gene discussed is FGFR1; the disease is Muenke syndrome.