Objectives: In IgG4-related disease, the relationship between pathological findings and relapse has not been well established. This study aimed to identify the clinical and pathological predictors of disease relapse in IgG4-RD. Methods: Patients with newly diagnosed IgG4-RD (n = 71) were enrolled between January 2011 and April 2020; all cases were pathologically confirmed. The clinical and pathological features were recorded in a database at baseline and each follow-up visit. Patients were followed up at least once a month via outpatient clinic examinations and telephone calls. Univariate and multivariate Cox regression analyses and receiver operating curve (ROC) analysis were used to identify the predictors of disease relapse and to assess their predictive value. Results: Over median follow-up of 26 (range, 6-123) months, 3/71 (4.2%) patients died. Of the remaining 68 patients, 47 (69.1%) patients had achieved clinical remission and 21 (30.9%) had suffered relapse at the last follow-up. The independent predictors of relapse were IgG4 ≥6.5 g/L (OR = 2.84, 95% CI: 1.11-7.23), IgG ≥20.8 g/L (OR = 4.11, 95% CI: 1.53-11.06), IgG4-RD responder index (RI) ≥9 (OR = 3.82, 95% CI: 1.28-11.37), and severe IgG4+ plasma cell infiltration (OR = 6.32, 95% CI: 1.79-22.41). A prognostic score developed using three of the identified predictors (IgG ≥20.8 g/L, IgG4-RD RI ≥9, and severe IgG4+ plasma cell infiltration) showed good value for predicting impending relapse (AUC, 0.806). Conclusions: In patients with IgG4-RD, IgG4 ≥6.5 g/L, IgG ≥20.8 g/L, IgG4-RD responder index (RI) ≥9, and severe IgG4+ plasma cell infiltration are predictors of relapse. Keywords: IgG4-related disease; relapse; prognostic factor Disclosures: None