Pfeiffer syndrome in humans, which shows similar craniofacial anomalies to those seen in Apert syndrome along with big toes and broad radially deviated thumbs (Giancotti et al., 2017), is due to a mutation in either FGFR1 (Pro252Arg) or FGFR2 (Trp290Cys, Try340Cys, Cys342Arg, or Ser351Cys, etc.)(Azoury et al., 2017). Here, FGFR2 is linked to Apert syndrome.