SAT-634 Navigating the Uncertainty: Atypical Diabetes Mellitus with Negative Biomarkers and Complex Management

Abstract Disclosure: A.J. Zaidi: None. W. Akhter: None. M. Fathima: None. J. Gilden: Novartis Pharmaceuticals. A. Khan: None. Background: Atypical forms of Diabetes Mellitus (DM) may present with unusual clinical features, challenging diagnosis and management. LADA (Latent Autoimmune DM in Adults), idiopathic, forms associated with beta-cell dysfunction, or ketosis-prone DM can present in adulthood with features that resemble type 1 DM but without a clear autoimmune etiology. We present the case of a young man who developed significant hyperglycemia but did not meet the typical criteria for either type 1 or type 2 DM, with significant retinopathy. Case Report: A 38-year-old African male with no known past medical history presented to the emergency room for malaise and was found to have a blood glucose (BG) level >700 mg/dL. The patient had no known prior or family history of DM. Over the preceding weeks, he noted polyuria, polydipsia, and fatigue. His clinical presentation raised concerns for Diabetic Ketoacidosis (DKA)/Hyperosmolar Hyperglycemic State (HHS), leading to ICU admission and initiation of insulin infusion. Laboratory showed normal bicarbonate levels, anion gap, and initial serum osmolarity of 309, negative blood ketones, although urine ketones were positive; HbA1c of 15%. He was discharged with insulin (Lantus 8 units and Novolog 2 units TID) and metformin (METF) 1000 mg BID.Two weeks later when he was evaluated in clinic he was only taking METF with small doses of short-acting insulin, as needed. Autoimmune testing was negative for GAD, IA-2, Zn transporter, and islet cell antibodies, which ruled out typical Type 1 diabetes; low c-peptide (0.18 units)(normal range 0.81-3.85 ng/ml) with low BG of 53 mg/dl. Continuous Glucose Monitoring (CGM) revealed episodes of hypoglycemia (HYPO). The METF dose was then decreased and eventually stopped. CGM continued to show premeal and exercise HYPO with 50s before dinner. He was also found to have advanced Diabetic retinopathy and proteinuria with Ur Albumin 4.4 mg/dl (normal 0.3-2.0) Clinical Course and Management: Off any antihyperglycemic agents, fasting BG average increased to around 200 mg/dl. with higher post meal BG. Patient was trialed with acarbose with no effect on BG, then a dipeptidyl peptidase-4 (DDP-4) inhibitor. However, BG increased to the 300’s. Insulin therapy was reintroduced. The final diagnosis for type of DM remains unclear. Conclusion: This case highlights the complexity involved in diagnosing and managing atypical forms of DM, including LADA, monogenic, and ketosis-prone DM. It is a spectrum, which may present with features of both type 1 and type 2 DM but lacks definitive biomarkers. Clinicians should consider the atypical forms in adult patients with new-onset diabetes and atypical presentations, especially when there is an absence of typical autoimmune markers. Management remains challenging. Presentation: Saturday, July 12, 2025