MON-552 - Arrested Development: When Autoimmune Type 1 Diabetes Presents in the Elderly

Background:
Latent autoimmune diabetes in adults (LADA) is classically characterized by a gradual progression to insulin dependence. In contrast, severe type 1 diabetes mellitus (T1DM) with rapid β-cell failure and diabetic ketoacidosis (DKA) is rarely reported in older adults. Recognition of this presentation is critical, as misclassification may delay appropriate insulin therapy.

Case Presentation:
We describe three patients aged ≥70 years who presented with new-onset, antibody-positive T1DM complicated by severe DKA. None had a prior diagnosis of diabetes, a personal or family history of autoimmune disease, immunosuppression, or exposure to immune checkpoint inhibitors.

Patient 1 was a 70-year-old woman (BMI 25 kg/m²) admitted with altered mental status following a flu-like illness, reporting weight loss, dry mouth, and blurred vision. Initial labs demonstrated glucose 521 mg/dL, β-hydroxybutyrate (BHB) 9.69 mmol/L, bicarbonate 5 mmol/L, and pH 6.83. She required insulin infusion and was transitioned to multiple daily injections (MDI). Initially discharged on basal insulin and metformin with islet autoantibodies pending, islet cell autoantibodies were subsequently positive at her endocrine transition clinic follow-up, and continuous glucose monitoring (CGM) revealed marked prandial hyperglycemia consistent with insulinopenia. She was ultimately transitioned to sensor-augmented automated insulin delivery.

Patient 2 was a 75-year-old man (BMI 25 kg/m²) presenting with altered mental status, weakness, and 20-lb weight loss, having been started on metformin one day prior to admission. Labs showed glucose 1200 mg/dL, β-hydroxybutyrate (BHB) 8.99 mmol/L, bicarbonate 4 mmol/L, and pH 7.11. His course was complicated by ischemic bowel requiring vasopressor support and exploratory laparotomy. Islet cell autoantibodies were positive prior to discharge, and he was transitioned to multiple daily injections (MDI). At follow-up, he remains managed on MDI with continuous glucose monitoring (CGM).

Patient 3 was a 74-year-old man (BMI 28 kg/m²) with nausea, vomiting, and polydipsia, presenting in DKA five weeks after being diagnosed with diabetes and started on metformin. Initial labs revealed glucose 739 mg/dL, BHB 12.39 mmol/L, bicarbonate 8 mmol/L, and pH 7.13. He was discharged on MDI and CGM, with autoimmune diabetes confirmed at his follow-up appointment.

Conclusion:
These cases demonstrate that severe autoimmune T1DM can occur in adults ≥70 years and may present with severe DKA, mimicking ketosis-prone type 2 diabetes. Early assessment of islet cell autoantibodies should be strongly considered in older patients with rapid-onset hyperglycemia or DKA to ensure timely diagnosis and appropriate insulin-based management.

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