At least 16 CHI-related pathogenic genes (ABCC8, KCNJ11, GLUD1, GCK, HADH, SLC16A1, UCP2, HNF4A, HNF1A, HK1, KCNQ1, CACNA1D, FOXA2, EIF2S3, PGM1, and PMM2) have been identified so far and are involved in the regulation of insulin secretion from pancreatic β-cells (1, 2). Here, PMM2 is linked to congenital isolated hyperinsulinism.