Serum interleukin‐10 level is increased and correlated positively with disease severity in patients with dipeptidyl peptidase‐4 inhibitor‐related bullous pemphigoid

Bullous pemphigoid (BP) is an autoimmune subepidermal blistering disease with a linear deposit of autoantibodies at the epidermal basement membrane zone. It was reported that diabetes patients who took a dipeptidyl peptidase-4 inhibitor (DPP4i), an oral antidiabetic drug, had an increased incidence of BP. However, data on DPP4i-related BP are limited. In our study, we measured serum levels of various cytokines using LEGENDplex and assessed correlations of these serum levels with clinical severity and laboratory data. Serum samples obtained from BP patients who visited our hospital from June 2016 to February 2023 were collected in this study. Patients' background, characteristics, and clinical data were retrospectively collected from their charts. Serum samples from 27 patients with DPP4i-unrelated BP, 17 patients with DPP4i-related BP, and 13 healthy controls were analyzed. Patients with DPP4i-related BP had lower score of Bullous Pemphigoid Disease Area Index (BPDAI)-erythema/urticaria, lower number of circulating eosinophils, and lower titer of anti-BP180 antibody than patients with DPP4i-unrelated BP. The serum interleukin (IL)-6 level was significantly higher in patients with DPP4i-related BP than in healthy controls (P = 0.0037). The serum IL-10 level was significantly higher in patients with DPP4i-related BP than in patients with DPP4i-unrelated BP and in healthy controls (P = 0.0006, P = 0.0448), and was positively correlated with the BPDAI-blister/erosions score (r = 0.757, P = 0.001), BPDAI-erythema/urticaria score (r = 0.616, P = 0.013), and BPDAI-total score (r = 0.833, P < 0.001) in patients with DPP4i-related BP. In conclusion, patients with DPP4i-related BP had increased serum levels of IL-6 and IL-10 compared with healthy controls and positive correlations between the serum IL-10 level and BPDAI scores reflecting clinical severity, indicating that the serum IL-10 level is a potential objective biomarker of disease severity in patients with DPP4i-related BP.