Sanger sequencing has been regularly used for genotyping of some common SD genes such as fibroblast growth factor receptor 3 (FGFR3) (thanatophoric dysplasia and achondroplasia), collagen type I alpha 1 chain (COL1A1) and collagen type I alpha 2 chain (COL1A2) (OI), diastrophic dysplasia sulfate transporter (DTDST) (diastrophic dysplasia and atelosteogenesis), and SRY-box 9 (SOX9) (camptomelic dysplasia), but this technique becomes costly and time-consuming when a great number of genes are tested before reaching a definite molecular diagnosis. The gene discussed is SOX9; the disease is thanatophoric dysplasia.