FGFR3 and skeletal dysplasia: Thanatophoric dysplasia (TD) is the most common lethal dominant skeletal dysplasia with an incidence of 2–3 per 100 000 births.1 It results from a mutation in the fibroblast growth factor receptor 3 (FGFR3) gene located on 4p16.3.2,3 There are several mutations known to cause TD, the most common being Arg248Cys, Tyr373Cys and Lys650Glu.3 TD may be divided into subtypes I and II, based both on molecular diagnosis and on clinical features, but there is considerable overlap between the two groups.