GCK and diabetes mellitus: If we focus on the most common MODY genes GCK, HNF1A and HNF4A, the prevalence in both our study (4%) and the Norwegian study (6%) is lower than the 15% seen in the Swedish National Cohort [3], likely explained by the latter including patients with all types of diabetes from paediatric clinics, with age at diagnosis of up to 18 years.