The near ultimate in genotype/phenotype correlation is provided by a few examples in which change in a single codon of a single gene results in the disorder. The phenotype in each case is as stereotypic as the genotype; mutations in other regions of the same gene result in different phenotypes. Striking examples include achondroplasia (MIM #100800) due to the c.1138G→A (Gly380Arg) mutation in the FGFR3 gene (MIM *134934.0001), Hutchinson-Gilford progeria syndrome (MIM #176670) due to the c.1824C→T (Gly608Gly) mutation in the LMNA gene (MIM *150330.0022), and fibrodysplasia ossificans progressiva (MIM #135100) due to the c.617G→A (Arg206His) mutation in the ACVR1 gene (MIM *102576.0001). In the case of achondroplasia, a few cases are due to a different nucleotide substitution in the same codon: c.1138G→C (Gly380Arg [MIM *134934.0002]). Similarly, a mutation in the same codon as is involved in the majority of cases of progeria has been found in some cases of that disorder: G→A (Gly608Ser [MIM *150330.0023]).