Dipeptidyl peptidase 4 inhibitor‐associated mucous membrane pemphigoid

Dipeptidyl peptidase 4 inhibitors (DPP‐4i) are associated with an increased risk of developing bullous pemphigoid (BP) in patients with diabetes. Autoantibodies targeting epitopes on the processed BP180, 120‐kDa (LAD‐1), and 97‐kDa (LABD97) linear immunoglobulin (Ig)A dermatosis antigens are the major autoantibodies in DPP‐4i‐associated BP. However, no case of mucous membrane pemphigoid (MMP) developing during treatment with DPP‐4i has been reported. We report a case of MMP associated with DPP‐4i. A man in his late 70s presented with oral mucous membrane erosion and a few blisters on his upper chest and back. He had used linagliptin for diabetes for over 1 year when he presented. The immunological characteristics were similar to DPP4i‐associated BP: higher reactivity to LAD‐1 and LABD97 than to the full‐length BP180. The aphthae achieved remission after oral linagliptin was replaced with sitagliptin. However, 6 months later, the aphthae relapsed and any DPP‐4i was discontinued. The aphthae disappeared, and now he is completely free from lesions associated with MMP. This case suggests that the DPP‐4i may have shared roles in the production of IgG antibodies to LAD‐1 or to LABD97 in the pathogenesis of DPP‐4i‐associated BP and MMP. Our case highlights the possibility of overlooking the mild MMP in DPP‐4i‐treated diabetes patients with mucosal lesions.