As well as mutations in FGFR2 and FGFR3, mutations in RET (causing multiple endocrine neoplasia types 2A and 2B), PTPN11 (causing Noonan syndrome) and HRAS (causing Costello syndrome) also belong to this group [reviewed in Goriely et al., 2009]. Here, FGFR3 is linked to Costello syndrome.