Achondroplasia is caused by a gain-of-function pathologic variant in the fibroblast growth factor receptor 3 (FGFR3) gene, with one amino acid substitution (glycine-to-arginine at position 380) responsible for 98% of all cases.4,5 Approximately 80% represent a de novo variant in FGFR36 on the paternal allele.7 Here, FGFR3 is linked to achondroplasia.