In our cohort, although a number of patients had monoallelic ABCC8/KCNJ11 mutations which usually results either in mild diazoxide responsive CHI or focal CHI if paternally inherited and associated with somatic loss of maternal 11p allele, detailed evaluation did not show response to medical therapy and histology showed diffuse disease. This evidence concerns the gene ABCC8 and congenital isolated hyperinsulinism.