In 2012, the Japan Diabetes Society showed that fulminant T1DM is diagnosed when all the following three findings are present: (1) occurrence of diabetic ketosis or ketoacidosis soon (about 7 days) after the onset of hyperglycemic symptoms (elevation of urinary and/or serum ketones at first visit), (2) plasma glucose ≥288 mg/dL and HbA1c < 8.7% at first visit, and (3) urinary C-peptide excretion <10 ug/d or fasting serum C-peptide level <0.3 ng/mL and serum C-peptide <0.5 ng/mL after intravenous glucagon (or after a meal) at onset (Imagawa et al., 2012). This evidence concerns the gene GCG and type 1 diabetes mellitus.