Japanese cases of type 1 thanatophoric dysplasia exclusively carry a C to T transition at nucleotide 742 of the fibroblast growth factor receptor 3 gene.

Type I thanatophoric dysplasia (TD) is typically a lethal neonatal dwarfism, but a limited number of cases of type I TD cases survive more than one year, suggesting genetic heterogeneity. In this study, we analyzed the fibroblast growth factor receptor 3 (FGFR3) gene in 5 Japanese cases of type I TD with clinical symptoms ranging from lethal to long-survival. In every case, nucleotide sequence analysis of cDNA revealed a C to T transition at nucleotide 742 (C742T) in one allele of the FGFR3 gene, suggesting that type I TD is a rather homogeneous genetic condition, irrespective of clinical course. No association was found between C742T and C882T, although both nucleotides changes were from CpG dinucleotide in a near location.