Pfeiffer syndrome is a genetic disorder characterized by the premature fusion of certain skull bones (craniosynostosis).This early fusion prevents the skull from growing normally and affects the shape of the head and face. Pfeiffer syndrome also affects bones in the hands and feet. mutation in either the FGFR1 or FGFR2 gene alters protein function and causes prolonged signaling, which can promote the premature fusion of skull bones and affect the development of bones in the hands and feet. Type 1 Pfeiffer syndrome is caused by mutations in either the FGFR1 or FGFR2 gene.