A 30-year-old woman was admitted because of severe thirst and polyuria at 21 weeks of gestation. After fetal demise, she developed disturbance of consciousness. Laboratory examinations showed hyperglycemia, ketoacidosis, low urinary C-peptide concentration, an almost normal HbA1c level, undetectable diabetes-related autoantibodies, and high serum pancreatic amylase. These findings indicated fulminant type 1 diabetes mellitus. Hyperamylasemia and diffuse swelling of the pancreas associated with peri-pancreatic effusion on computed tomography indicated severe acute pancreatitis. After intensive therapy by infusion of fluid, insulin and nafamostat, she recovered and was discharged with insulin supplementation. Fulminant type 1 diabetes mellitus, especially pregnancy-associated fulminant type 1 diabetes mellitus, needs to be recognized because of its abrupt onset during pregnancy and the poor prognosis for the fetus.
