GCK and congenital isolated hyperinsulinism: In our cohort of patients with CHI, 32.8% were noted to have disease-causing mutations: 16 (25%) patients were positive for ABCC8 mutations; five (7.8%) were positive for GLUD1 mutations; and 44 (67%) were negative for GCK, GLUD1, ABCC8 and KCNJ11 mutations in the gene analysis.