PRRT2 and spondylocostal dysostosis: In case 2, the fetus had a 0.58 Mb deletion in the 16p11.2 region, which contained 22 OMIM genes, including PRRT2, TBX6, and KCTD13. A mutation in TBX6 is associated with spondylocostal dysostosis, with clinical phenotypes including segmentation defect of vertebrae, irregular arrangement of ribs, and reduction of ribs.