In contrast, as shown in Figure 1b, serum levels of APRIL in patients with IgG4-RD before GC therapy (n = 13, 3.736 ± 3.271 ng/mL) were significantly higher than those in the healthy controls (n = 10, 1.327 ± 1.259 ng/mL) (P < 0.01), however, unlike BAFF, the levels were significantly lower than those in patients with pSS (n = 13, 11.250 ± 7.418 ng/mL) (P < 0.01). This evidence concerns the gene TNFSF13 and peeling skin syndrome.