Serum levels of IL-13 in patients with IgG4-RD (3.99 ± 6.15 pg/mL) were comparable to those in HC (3.18 ± 2.61 pg/mL; P = 0.524), and both were significantly lower than in patients with pSS (10.05 ± 13.99 pg/mL; Figure 5D). This evidence concerns the gene IL13 and immunoglobulin G4-related sclerosing disease.