SAT-627 Seronegative Type 1 Diabetes Mellitus in a Young Adult

Abstract Disclosure: S. Lukose: None. Y. Rapoport: None. S. Obici: None. Introduction: Seronegative Type 1 Diabetes Mellitus (T1DM) is a form of diabetes in which patients exhibit the classic clinical features of type 1 diabetes but lack detectable autoimmune antibodies typically associated with pancreatic beta-cell destruction. This case underscores the importance of considering seronegative T1DM in patients presenting with symptoms suggestive of type 1 diabetes, even when autoantibody tests are negative. Clinical Case: The patient is a 25-year-old woman with a medical history of IgA nephropathy, hypothyroidism secondary to Hashimoto’s thyroiditis, hidradenitis suppurativa, and obesity who presented with a vulvar abscess. At presentation, her laboratory results were consistent with diabetic ketoacidosis (DKA), with a glucose level of 564 mg/dL, bicarbonate of 12 mEq/L, anion gap (AG) of 25, beta-hydroxybutyrate of 7.24 mmol/L, HbA1C of 12.8%, and a venous blood gas (VBG) pH of 7.22. Autoantibody testing, including glutamic acid decarboxylase antibody, zinc transporter 8 antibody, islet antigen 2 antibody and insulin antibody were all negative. C-peptide level collected a few days after admission were 0.6 ng/mL. The patient was treated with intravenous fluids, insulin infusion, and antibiotics. Interestingly, the patient had experienced her first episode of DKA four years earlier at the age of 21, when she presented with a perianal abscess. Laboratory results at that time showed a glucose level of 469 mg/dL, bicarbonate of 11 mEq/L, AG of 24, beta-hydroxybutyrate of 6.41 mmol/L, HbA1C of 11.4%, and VBG pH of 7.23. Autoantibody testing were also negative at that time. She was diagnosed with type 2 diabetes and discharged on a regimen of multiple daily insulin injections. However, the patient discontinued insulin therapy after 2-3 months due to episodes of hypoglycemia, vision changes, and dizziness. During a documented six-month period without medication, her HbA1C remained stable between 4.9% and 5.0%. Given her clinical course, the presence of two episodes of DKA, and history of autoimmune diseases, her diagnosis was reevaluated, and she was ultimately diagnosed with type 1 diabetes mellitus. Conclusion: In patients presenting with DKA and negative autoantibodies, seronegative T1DM should be considered as a potential diagnosis, alongside conditions such as ketone-prone type 2 diabetes and monogenic diabetes. Although the absence of autoantibodies complicates the diagnostic process, the presence of a honeymoon period and recurrent episodes of DKA make type 1 diabetes a more likely diagnosis for this patient. This case highlights the importance of including seronegative T1DM in the differential diagnosis of patients with recurrent DKA, particularly those who experience a "honeymoon phase" after initial treatment. Early recognition and management are critical to optimizing outcomes for these patients. Presentation: Saturday, July 12, 2025