To date, ten genes have been linked to isolated CHI, explaining 45–55% of the cases (ABCC8, KCNJ11, GLUD1, GCK, HADH, HNF1A, HNF4A, SLC16A1, UCP2, HK1) and more than 28 genes or chromosomal abnormalities have been reported for syndromic CHI. Here, HK1 is linked to congenital isolated hyperinsulinism.