Gain-of-function mutations of FGFR3 cause several short-limbed skeletal dysplasias such as hypochondroplasia (HCH) [8], severe ACH with developmental delay and acanthosis nigricans (SADDAN) [9], and thanatophoric dysplasia (TD) types I and II [10]. This evidence concerns the gene FGFR3 and Severe achondroplasia - developmental delay - acanthosis nigricans.