Decrease in eosinophils infiltrating into the skin of patients with dipeptidyl peptidase-4 inhibitor-related bullous pemphigoid

Bullous pemphigoid (BP) is an acquired autoimmune blistering disease in which autoantibodies against epitopes in the basement membrane zone of the skin such as BP180 or BP230 are produced. Dipeptidyl peptidase (DPP)-4 inhibitors have become commonly used to treat diabetes. As DPP-4 inhibitors are more commonly prescribed for diabetes, BP related to DPP-4 inhibitors has been reported and has attracted attention. Therefore, we retrospectively investigated patients who were diagnosed with BP in order to examine characteristics of DPP-4 inhibitor-related BP (nine patients; median age, 85 years) in comparison with non-DPP-4 inhibitor-related BP (21; median age, 85 years). There was no significant difference in Bullous Pemphigoid Disease Area Index between DPP-4 inhibitor-related BP patients and non-DPP-4 inhibitor-related BP patients, except for erosions/blisters score in mucosa. Laboratory tests revealed no significant differences between DPP-4 inhibitor-related BP patients and non-DPP-4 inhibitor-related BP patients in total white blood cell count, eosinophil count, neutrophil count and the titer of anti-BP180 antibody. The number of eosinophils infiltrating into the skin was significantly lower in patients with DPP4 inhibitor-related BP than in patients with non-DPP4 inhibitor-related BP. Our results showed that DPP-4 inhibitor-related BP has some distinct pathological characteristics from BP not associated with DPP-4 inhibitor.