Neonatal diabetes, transient (TND) or permanent (PND) is a rare disease, with a reported frequency of 1/300,000. If establishing a diagnosis is quite easy, treatment remains challenging during childhood. Understanding of physiopathology increased this last decade, as many mutations in genes playing critical roles in the development of pancreas, have been described: the most common are chromosome 6q anomalies in the case of TND, and mutations in KCNJ11 and ABCC8 genes encoding the subunit of the insulin cell potassium channel in the case of PND. We report on 2 peculiar stories: the first one is the unique case of a newborn with isodisomy of chromosome 6, methylmalonic acidemia and pancreatic beta cell agenesis, who died on the 16th day of life. The second one is the longest follow-up ever described, 38-year, of a permanent neonatal diabetes mellitus without complications, except for rare micro-aneurysms, in spite of insufficient metabolic control.