SAT-230 Unusual Presentation Of Autoimmune Polyendocrine Syndrome Type 1 With Positive Gad65 Antibodies But Preserved Pancreatic Function Despite Severe Necrotizing Pancreatitis: A Case Report

Abstract Disclosure: P.S. Sidhu: None. L.L. Ponce Rosas: None. A.M. Zia: None. J. Arriaga: None. C. Peñaherrera: None. A. Abualnil: None. Background: Autoimmune Polyendocrine Syndrome Type 1 (APS-1), also known as Autoimmune Polyendocrinopathy-Candidiasis-Ectodermal Dystrophy (APECED), is a rare autosomal recessive disorder characterized by autoimmune destruction of multiple endocrine organs, classically presenting with chronic mucocutaneous candidiasis, hypoparathyroidism, and adrenal insufficiency. Type 1 diabetes mellitus (T1DM) occurs in 18-33% of APS-1 patients, typically in the second or third decade.Case Presentation: A 23-year-old male with APS-1 diagnosed at age 9 presented with the classic triad of Addison's disease, oral candidiasis, and hypoparathyroidism. His medical history includes multiple abdominal surgeries and peripheral vascular disease requiring stenting. In December 2023, he developed severe necrotizing pancreatitis due to choledocholithiasis requiring ERCP, complicated by duodenal perforation and fistula formation necessitating necrosectomy.Remarkably, despite positive GAD65 autoantibodies (17 IU/mL) and severe pancreatic insult from necrotizing pancreatitis, the patient maintains normoglycemia with an HbA1c of 5.5% and no evidence of diabetes mellitus, with preserved beta-cell function demonstrated by normal C-peptide level (3.13 ng/mL). Current management includes hydrocortisone 20 mg AM/10 mg PM, fludrocortisone 0.1 mg daily for Addison's disease, and calcitriol 1.5 mcg daily with ergocalciferol 50,000 IU weekly for hypoparathyroidism. Recent laboratory values show calcium 11.1 mg/dL, PTH 23 pg/mL, and 25-OH vitamin D 39.8 ng/mL.Discussion: This case highlights the preservation of pancreatic endocrine function despite GAD65 autoantibodies (a significant predictor of T1DM in APS-1) and severe necrotizing pancreatitis. These observations suggest potential protective mechanisms against beta-cell destruction despite autoimmune predisposition and direct pancreatic injury. Conclusion: This unusual APS-1 phenotype demonstrates preserved pancreatic endocrine function despite significant risk factors for diabetes. The isolated GAD65 positivity without other pancreatic autoantibodies influenced clinical management. Further investigation into protective factors against beta-cell destruction could provide insights into autoimmune diabetes prevention mechanisms. This case emphasizes the importance of monitoring for evolving endocrinopathies in APS-1 patients throughout their lifetime. Presentation: Saturday, July 12, 2025