Mutations in the ABCC8 and KCNJ11 genes, which encode subunits of the ATP-sensitive potassium channel (KATP) in the pancreatic β-cell, are identified in approximately 40 to 45% of these patients and are responsible for most (82%) of the severe diazoxide-unresponsive CHI. This evidence concerns the gene ABCC8 and congenital isolated hyperinsulinism.