As shown in Figure 1a, serum levels of BAFF in patients with IgG4-RD before GC therapy (n = 13, 1.512 ± 0.393 ng/mL) were significantly higher than those in healthy controls (n = 10, 0.904 ± 0.262 ng/mL) (P < 0.01), and there were no significant differences in the serum levels of BAFF between patients with IgG4-RD before GC therapy and patients with pSS (n = 13, 1.820 ± 0.954 ng/mL) (P = 0.383). Here, TNFSF13B is linked to immunoglobulin G4-related sclerosing disease.