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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.

Generalized pustular psoriasis (GPP) is a systemic inflammatory disease that presents with erythema and sterile pustules, pathologically characterized by Kogoj's spongiform pustules. GPP is sometimes accompanied by mucosal involvement, and the most common lesion is on the tongue. IL36RN mutation was found to contribute to the pathogenesis of GPP especially in patients who develop GPP without a past medical history of psoriasis vulgaris. The association of IL36RN mutation with mucosal involvement in GPP is controversial. We herein report a 60-year-old male GPP patient with no past history of plaque psoriasis presenting with not only severe skin lesions and arthritis but also severe mucosal involvements of pharyngeal and gastrointestinal lesions, which led to gastrointestinal bleeding. Our case did not have any mutation in the IL36RN gene. We should be aware that severe GPP can cause gastrointestinal bleeding. The relevancy of IL36RN mutation with mucosal involvement in GPP remains to be elucidated.