This rare disease is caused by missense mutations in the FGFR3 gene (4p16.3; MIM 134934) encoding fibroblast growth factor receptor 3 as opposed to the differently located FGFR2 gene (10q26.13; MIM 176943) which is linked to the classic phenotype of Crouzon syndrome (CFD1; 10q26.13; MIM 123500). This evidence concerns the gene FGFR3 and Crouzon syndrome.