A decade of clinical course and prognostic determinants in type 1 autoimmune pancreatitis: insights from a 10-year longitudinal multicenter retrospective study

Background Type 1 autoimmune pancreatitis (AIP) is a unique form of pancreatitis characterized by IgG4-related inflammation and corticosteroid (CS) responsiveness, but long-term outcomes remain unclear. We evaluated 10-year relapse, malignancy, metabolic/nutritional changes, and survival. Methods We retrospectively analyzed 83 CS-treated patients with type 1 AIP followed for ≥ 10 years or until death, assessing: relapse and risk factors; standardized incidence ratios (SIRs) and risk factors for malignancies; 10-year changes in HbA1c and serum albumin; CS-related adverse events; and overall survival (OS). Results Cumulative relapse rates at 1, 3, 5, 7, and 10 years were 11.0%, 26.9%, 38.3%, 50.0%, and 56.9%. CS discontinuation independently predicted relapse, whereas serum IgG4 normal at diagnosis or normalized after CS was protective. Overall malignancy risk was not increased (SIR 1.00; 95%CI 0.59–1.42), while pancreatic cancer (PC) showed a numerically higher SIR (1.98 overall; 2.96 ≥ 5 years postdiagnosis). In 72 patients with 10-year laboratory follow-up, HbA1c improved at 3 years but tended to worsen at 10 years, and serum albumin declined by 10 years (mean − 0.27 g/dL), exceeding age-related norms. Preexisting diabetes attenuated albumin decline. Ten-year survival was 85.5%, and CS maintenance was associated with better OS. Conclusions Type 1 AIP shows progressive relapse and metabolic deterioration over a decade, while CS maintenance and IgG4 normalization confer long-term protection. Although the overall risk of malignancy was not increased, the incidence of PC during late follow-up was slightly higher. These findings highlight the need for continuous monitoring for relapse, PC, and nutritional decline in AIP management.