The underlying cause of ACH is a specific activating mutation of the fibroblast growth factor receptor-3 (FGFR3) gene at position 1138 that occurs in two variants (1138G > A and 1138G > C), resulting in the substitution of arginine with glycine at position 380 (G380R) in the transmembrane domain of the FGFR3 protein [1, 2]. The gene discussed is FGFR3; the disease is achondroplasia.