From Type 2 Diabetes Mellitus to Autoimmune Failure: Euglycemic Diabetic Ketoacidosis Revealing Latent Autoimmune Diabetes in Adults

Latent autoimmune diabetes in adults (LADA) is a slowly progressive form of autoimmune diabetes that is frequently misclassified as type 2 diabetes mellitus (T2DM) because of its gradual onset and initial responsiveness to oral hypoglycemic agents. This misclassification may delay appropriate insulin therapy and expose patients to medications that increase the risk of metabolic complications. Sodium glucose cotransporter-2 (SGLT2) inhibitors have been increasingly associated with euglycemic diabetic ketoacidosis (DKA), particularly in individuals with underlying insulin deficiency. Several reports describe euglycemic DKA as the presenting manifestation of previously unrecognized LADA. We report a case of a 55-year-old man with a nine-year history of presumed T2DM treated with metformin and canagliflozin who presented with vomiting, dehydration, and metabolic acidosis. Laboratory evaluation revealed high anion gap metabolic acidosis and marked ketosis despite only modest hyperglycemia, consistent with euglycemic DKA. The patient was successfully treated with intravenous fluids, insulin infusion, and electrolyte replacement. Further evaluation demonstrated markedly elevated anti-glutamic acid decarboxylase (GAD65) antibodies and reduced C-peptide levels, confirming autoimmune β-cell failure consistent with LADA. The SGLT2 inhibitor was discontinued, and the patient was transitioned to a basal-bolus insulin regimen with structured diabetes education. This case highlights how slowly progressive autoimmune diabetes may remain unrecognized for years and may be unmasked by metabolic stressors or SGLT2 inhibitor therapy. Clinicians should consider autoimmune diabetes in adults with atypical diabetes phenotypes or unexpected ketoacidosis and use antibody testing and C-peptide measurement to guide diagnosis and management.