Cutaneous autoimmune blistering disease during mirikizumab therapy in a patient with ulcerative colitis: a new potential trigger?

Autoimmune blistering diseases (AIBDs) may occur as adverse effects of various therapies, including biologics. Data on their association with IL-23 inhibitors in ulcerative colitis (UC) remain limited. We report the case of a 59-year-old man with UC who developed pruritic cutaneous bullae emerging within days following mirikizumab infusion. Histopathological examination and direct immunofluorescence demonstrated findings consistent with an AIBD. Following the withdrawal of mirikizumab, the residual cutaneous lesions progressively improved under corticosteroid therapy, suggesting a temporal association with the biologic exposure. This case highlights that mirikizumab may represent a potential trigger of an AIBD in susceptible individuals with UC. Clinicians should be aware of this rare but relevant complication to ensure timely recognition and management.