Crouzon syndrome and Pfeiffer syndrome are both craniosynostosis syndromes caused by a mutated FGFR2 gene. Three types of Pfeiffer syndrome exist with varying degrees of severity. With Pfeiffer syndrome, your baby has the craniofacial characteristics of Crouzon syndrome. They also have short, broad big toes and thumbs. In Pfeiffer syndrome types 2 and 3, the craniofacial characteristics are more severe. Mental and neurological problems are more likely, as well.