S5424 IgG4 Cholangiopathy: An Overlooked Clinical Correlate to Acute Pancreatitis

Introduction: IgG4-related disease is a fibro-inflammatory autoimmune condition that commonly affects the pancreas and biliary tree. This case highlights IgG4-related cholangiopathy as an underrecognized etiology of biliary strictures and pancreatitis, emphasizing the importance of maintaining a broad differential in patients with atypical presentations. Case Description/Methods: A 61-year-old man with history of treated hepatitis C, obesity, and prior cholecystectomy presented with recurrent abdominal pain, pruritus, jaundice, nausea, and fatigue. He had been recently hospitalized for acute pancreatitis with elevated liver chemistries. No history of alcohol use. On presentation, labs revealed blood glucose of 524 mg/dL, alkaline phosphatase 221 U/L, aspartate aminotransferase 137 U/L, ALT 391 U/L, and total bilirubin 3.9 mg/dL, lipase 38 U/L. Magnetic resonance cholangiopancreatography revealed mild pancreatic duct dilation and intrahepatic biliary changes. Endoscopic retrograde cholangiopancreatography identified a 15 mm distal common bile duct (CBD) stricture with proximal dilation. Biliary sphincterotomy was performed, followed by biopsies of the distal CBD, and placement of a 10 Fr by 7 cm plastic stent. Histopathology showed increased IgG4-positive plasma cells, and serum IgG4 was elevated at 241 mg/dL (ULN: 123 mg/dL). There was no evidence of malignancy. After multidisciplinary care discussion, the patient was started on prednisone and discharged with outpatient follow-up. Over subsequent months, steroids were tapered and was started on rituximab. At 1 year, he demonstrated complete resolution of symptoms and normalization of biliary anatomy. Discussion: This case illustrates a rare presentation of IgG4-related cholangiopathy without other systemic manifestations, such as tubulointerstitial nephritis. Notably, his previous pancreatitis episodes may have been early signs of IgG4-related disease, misattributed to gallbladder pathology. This underscores the importance of considering IgG4-RD in patients with recurrent pancreatitis or biliary disease when common causes are excluded. Multidisciplinary collaboration was critical to timely diagnosis and treatment.