ABCC8 and Down syndrome: In keeping with our findings, screening of the known genes identified an ABCC8 mutation in a single individual whilst the four mutation negative individuals had non‐genetic risk factors for HI which could be attributed to the Down syndrome phenotype: extreme prematurity and cardiac insufficiency, IUGR, gastric surgery/fundoplication, and stress due to congenital heart defects (personal communication Huopio and Männistö).