FGFR3 and achondroplasia: In achondroplasia, the FGFR3 gene has a point mutation at nucleotide 1138 resulting from either G—A or G—>C.4 Approximately 98% of the ACH cases are caused by variation at nucleotide position 1138, with 97% involving a (c1138) G — A mutation and 1% involving a (c1138) G — C mutation.5,6