Monogenic forms of diabetes are caused by mutations in single genes and constitute a yet-unknown fraction of all diabetes.
MODY is the most common type of monogenic diabetes and can be caused by mutations in at least 13 genes [1]. The clinical picture is characterised by autosomal dominant inheritance, onset before 25–35 years of age, normal body weight, primary beta cell dysfunction and lack of markers of autoimmune diabetes. In the Norwegian MODY Registry, the distribution of the most common MODY forms among patients with a molecular diagnosis of MODY is as follows: HNF1A-MODY 53%, GCK-MODY 30%, HNF4A-MODY 7.5% and HNF1B-MODY 5.6%, while several other forms are very rare [2–4].