Abstract Disclosure: D. Bondarenko: None. D. Deyar: None. R. Nadeem: None. M. Herrera: None. L.E. Arzeno: None. Introduction: Type 1 diabetes mellitus (T1DM) stems from insulin deficiency due to islet-related autoantibodies. Misclassification of T1DM as type 2 diabetes mellitus (T2DM) occurs in 40% of those developing T1DM after age 30. Fulminant T1DM (FT1DM), described in East Asia, exhibits rapid progression and is diagnosed by ketosis, blood glucose ≥288 mg/dL, HgbA1c <8.7%, and fasting C-peptide <0.3 ng/mL. We present a case of rapidly progressing T1DM in a white male presenting as a hyperglycemic crisis (HC) complicated by multiorgan failure and bowel ischemia. CASE:A 52-year-old male, T2DM diagnosed by HgbA1c of 8% (normal <5.7%) 1 month prior, presented to the emergency room obtunded with two days of nausea and vomiting. Vital signs were normal other than tachycardia and tachypnea. Blood work showed pH 7.0 (normal 7.31-7.41), creatinine 4.58 mg/dL (0.7-1.3 mg/dL), glucose >1500 mg/dL (normal 65-139 mg/dL), beta-hydroxybutyrate 114.7 mg/dL (normal 0.2-2.8 mg/dL), lactate 5.7 mmol/L (normal 0.5-2 mmol/L), serum osmolarity 438 mOsmol/kg (normal 275-295 mOsmol/kg), WBC 26.2 B/L (4-11 B/L) and 4% bands (normal 0%), Hgb A1c 17.1% , C-peptide 0.11 ng/mL (0.8 - 3.85 ng/mL), GAD65 1:600 - 1:1200 (normal < 1:600). He was intubated Day 1-5. HC was treated with intravenous (IV) fluids and IV insulin infusion. He transitioned to subcutaneous insulin by Day 2. 10 days hemodialysis achieved renal recovery. He was diagnosed with latent autoimmune diabetes of adult (LADA). No triggers were identified for his HC. From Day 1, his abdominal exam was notable for guarding. Initial abdominal computed tomography (CT) was normal. Abdominal pain and distension persisted despite normalized blood work. Repeat CT showed ileus vs obstruction. Surgery on Day 12 showed multifocal bowel ischemia requiring surgical resection. Conclusion: FT1DM is a subtype of T1DM seen in Asia characterized by rapid β-cell destruction with hyperglycemia and ketoacidosis. LADA subset of T1DM manifests in adults and may take up to three years to progress to insulin dependence. Triggers for both include autoimmunity, infections, and pregnancy. HC has been associated with increased risk of occlusive and nonocclusive bowel ischemia. While this case does not meet all criteria of FT1DM, the rapid progression of the HgbA1c and disease severity is an unusual presentation of LADA. Raising awareness of the complications of this severe metabolic disorder can improve timely interventions and medical outcomes. Presentation: 6/1/2024