KCNJ11 and congenital isolated hyperinsulinism: Focal CHI is strongly associated with a heterozygous, paternally inherited KATP-channel germline mutation, as this combined with a somatic loss of heterozygosity in chromosome 11p15 in a focal region of the pancreas results in hemizygosity of the paternal ABCC8/KCNJ11 mutation and loss of maternally expressed tumor suppressors [1].