Elevated CA19-9 in IgG4-Related Autoimmune Pancreatitis: A Single-Center Retrospective Cohort Study

Background: IgG4-related autoimmune pancreatitis (IgG4-AIP) is a rare autoimmune pancreatic disorder, with elevated carbohydrate antigen 19– 9 (CA19-9) observed in some patients. Objective: This study aims to compare the clinical features of IgG4-AIP patients with elevated versus normal CA19-9 levels to clarify the clinical significance of CA19-9 in this condition. Methods: This study conducted a retrospective analysis of the clinical data of 41 patients with IgG4-AIP who underwent CA19-9 testing at Yichang Central People’s Hospital from January 2019 to April 2025. In this study, the normal reference range for CA19-9 levels was defined as 0 to 39 U/mL. Results: Among the 41 patients with IgG4-AIP, 23 patients (56.10%) had normal CA19-9 levels, while 18 patients (43.90%) exhibited elevated CA19-9 levels. Patients with elevated CA19-9 levels were more likely to be misdiagnosed as having pancreatic tumors (55.56% vs. 13.04%) and had a higher incidence of bile duct involvement (88.89% vs. 26.09%), whereas the incidence of lymph node involvement (22.22% vs. 56.52%) was lower ( P < 0.05). Compared to the normal CA19-9 group, patients in the elevated CA19-9 group had significantly higher levels of total bilirubin (TBIL), direct bilirubin (DBIL), alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), alkaline phosphatase (ALP), and complement C3 (C3) ( P < 0.05). Additionally, CA19-9 levels demonstrated a moderate positive correlation with TBIL, DBIL, ALT, AST, GGT, and ALP ( P < 0.05). However, no significant correlation was found between CA19-9 levels and C3 or serum immunoglobulin G4 (IgG4) levels ( P > 0.05). Conclusion: Patients with elevated CA19-9 levels in IgG4-AIP exhibit more complex clinical features. Clinicians should consider CA19-9 level differences when evaluating and managing IgG4-AIP patients to guide personalized diagnostic and therapeutic strategies. Keywords: IgG4-related autoimmune pancreatitis, IgG4-related disease, carbohydrate antigen 19-9