Ach is an autosomal dominant disorder caused by a mutation in the short arm of chromosome 4 that affects the fibroblast growth factor receptor 3 (FGFR3) gene.1, 5 Different mutations of FGFR3 can cause hypochondroplasia, Ach, severe Ach with developmental delay and acanthosis nigricans, thanatophoric dysplasia, and many other diseases that manifest as short stature.3 This evidence concerns the gene FGFR3 and hypochondroplasia.