Development of bullous pemphigoid during treatment of psoriatic onycho‐pachydermo periostitis with ustekinumab

Ustekinumab is a human monoclonal antibody that specifically binds to the p40 subunit of interleukin (IL)-12 and IL-23, inhibiting the activity of both cytokines, thereby blocking the T-helper (Th)1 and Th17 inflammatory pathways. While biologic agents have dramatically changed the strategies of psoriasis treatment, increasing cases of autoimmune diseases during the use of such agents have been reported. We experienced a case of bullous pemphigoid occurring during treatment of a rare variant of psoriatic arthritis, psoriatic onycho-pachydermo periostitis with ustekinumab. Only six cases of autoimmune blistering diseases during treatment with biologic agents have ever been reported including our case, and we herein review the published work of these cases. Dermatologists must be attentive to the possibility of autoimmune blistering diseases during ustekinumab treatment.