Inactivating mutations in the genes encoding the two subunits of the ß-cell ATP-sensitive potassium channel (KATP channel), ABCC8 and KCNJ11 (encoding SUR-1 and Kir6.2, respectively), cause the most common and severe form of hyperinsulinism, although mutations in ABCC8 are more common[4,5]. Here, KCNJ11 is linked to hyperinsulinism.