In the present study, one affected family member (II-2) with documented hypoglycaemia in infancy had developed type 2 diabetes by the time of examination (without previous pancreatectomy), as has been reported in three pedigrees for carriers of the activating GCK variants p.Val455Met, p.Gly68Val or p.Thr103Ser, respectively [12, 40–42]. The gene discussed is GCK; the disease is type 2 diabetes mellitus.