FGFR3 and achondroplasia: Achondroplasia (ACH) and hypochondroplasia (HCH), the two most common types of dwarfism, are each caused by FGFR3 gain-of-function mutations that result in increased FGFR3 signaling, which disrupts chondrogenesis and osteogenesis, resulting in disproportionately shortened long bones.