The importance of FGFR3 in early bone development was established from the association of point mutations in FGFR3 with dominant chondrodysplasias ranging in severity from mild (hypochondroplasia [HCH] and achondroplasia [ACH]) to severe (thanatophoric dysplasia [TD]), [21], [22]. This evidence concerns the gene FGFR3 and thanatophoric dysplasia.