FGFR3 gene mutation is the major pathogeny of skeletal dysplasia, including achondroplasia (ACH, OMIM: 100,800), hypochondroplasia (HCH, OMIM: 146,000), thanatophoric dysplasia types 1 (TD1) and 2 (TD2), and severe ACH with developmental delay and acanthosis nigricans (SADDAN). The gene discussed is FGFR3; the disease is skeletal dysplasia.