S3588 Unmasking Type II Autoimmune Pancreatitis in Ulcerative Colitis: A Diagnostic and Therapeutic Challenge

Introduction: Ulcerative colitis (UC) is often linked with extra-intestinal manifestations but Type II autoimmune pancreatitis (AIP-II) – remains under-recognized and rare. AIP-II is a steroid-responsive, immune-mediated form of pancreatitis that lacks IgG4 & systemic organ involvement, or reliable biomarkers. Its diagnosis is challenging due to its overlap with idiopathic pancreatitis and limitations of tissue acquisition in acute settings. We present a compelling case of probable AIP-II in a young patient with UC and axial spondyloarthritis (AS), highlighting key diagnostic considerations and the therapeutic utility of immunosuppression. Case Description/Methods: A 31-year-old man with a 2-year history of UC and HLA-B27-positive AS, previously treated with adalimumab, presented with acute epigastric pain and vomiting. He had 2 prior episodes of idiopathic acute pancreatitis. There was no history of alcohol or tobacco use, drug-induced pancreatitis, or trauma. Laboratory testing revealed leucocytosis and marked lipase elevation (3750 U/L), with normal hepatic and renal profiles. Infectious, autoimmune, genetic (PRSS1, SPINK1, CFTR, CPA1), and oncologic panels were unremarkable; serum IgG4 was within normal limits. Colonoscopy revealed active pancolitis (UCEIS 3/8), and histopathology confirmed moderate active colitis. Cross-sectional imaging (computed tomography, magnetic resonance cholangiopancreatography [MRCP]) and endoscopic ultrasound showed interstitial pancreatitis without necrosis, ductal stones, or mass lesions. Notably, MRCP identified multifocal pancreatic duct strictures and right hepatic duct irregularities, with no evidence of primary sclerosing cholangitis. Given the clinical phenotype, radiologic findings, negative biomarkers, and coexisting UC, a diagnosis of probable AIP-II was made in accordance with the ICDC. Pancreatic biopsy was deferred to avoid exacerbation. The patient was initiated on oral prednisolone, 5-ASA, and tofacitinib. Clinical resolution occurred within 5 days. Follow-up imaging after 2 weeks demonstrated complete resolution of pancreatic and biliary strictures. Lipase and CA 19-9 normalized. Discussion: This case underscores the importance of considering AIP-II in patients with UC and recurrent idiopathic pancreatitis. Early diagnosis guided by clinical, serologic, and radiologic synthesis – rather than histology alone – is critical. Prompt steroid therapy can lead to rapid remission and obviate unnecessary interventions. Heightened awareness of AIP-II as a rare but treatable extraintestinal manifestation of UC is essential for improving outcomes.