FGFR2 and bent bone dysplasia: FGFR2 gain-of-function mutations contribute to Apert syndrome, Beare–Stevenson syndrome, Crouzon syndrome, Pfeiffer syndrome and bent bone dysplasia (Box 2), each involving suture fusion (Jabs et al., 1994; Lajeunie et al., 1995; Merrill et al., 2012; Przylepa et al., 1996; Reardon et al., 1994; Rutland et al., 1995; Wilkie et al., 1995).