In outbred Caucasian populations, heterozygous mutations in KCNJ11, ABCC8 or INS genes may account for almost 40% of PNDM, compared to less than 5% in consanguineous families; in contrast homozygous mutations at INS, GCK or ABCC8 genes may account for a total of 30% and EIF2AK3 mutations for almost 25% of PNDM patients in consanguineous families [4]. The gene discussed is GCK; the disease is permanent neonatal diabetes mellitus.