Diffuse CHI (Di-CHI) is characterized by autosomal recessive or (less frequently) dominant inheritance, whereas focal CHI (Fo-CHI) is due to a germline paternal mutation (in the ABCC8 or KCNJ11 gene) in addition to a somatic loss of the maternally-derived chromosome 11p15.1 region in pancreatic β-cells [2]. This evidence concerns the gene KCNJ11 and congenital isolated hyperinsulinism.