Diabetic Ketoacidosis as the Presenting Feature of Type 3C Diabetes: A Case Report of Missed Chronic Calcific Pancreatitis

Type 3C Diabetes Mellitus (T3cDM), also termed pancreatogenic or pancreatic diabetes, arises from exocrine pancreatic disease, yet remains widely underdiagnosed and misclassified as Type 2 Diabetes Mellitus (T2DM). This misclassification carries significant therapeutic consequences, as standard oral hypoglycaemic regimens used in T2DM are often inappropriate or contraindicated in the setting of pancreatic exocrine failure. We report a 38-year-old male driver with a five-year history of diabetes mellitus managed on tablet metformin 500 mg and glimepiride 1 mg twice daily, who presented with epigastric pain, low-grade fever, and incidental post-varicella cutaneous lesions. Investigations revealed metabolic acidosis with an elevated anion gap consistent with mild Diabetic Ketoacidosis (DKA), hyponatraemia, hypokalaemia, and a markedly elevated C-Reactive Protein (CRP >300 mg/L). Retrospective analysis confirmed that this patient had been inappropriately treated with oral hypoglycaemic agents contraindicated in pancreatogenic diabetes. In-hospital management included intravenous fluid resuscitation, broad-spectrum antibiotics, continuous actrapid insulin infusion, and subsequent initiation of basal insulin glargine once the metabolic acidosis resolved. The case highlights prolonged misclassification of T3cDM as T2DM, atypical DKA presentation, and the diagnostic limitation of normal-to-low pancreatic enzymes.