Drug-Induced Bullous Pemphigoid Triggered by Immune Checkpoint Inhibitor Opdualag in an Elderly Patient With Recurrent Metastatic Melanoma: A Case Report and Treatment Course With Dupilumab.

Bullous pemphigoid (BP) is an autoimmune subepidermal blistering disorder most commonly affecting elderly individuals and may be triggered by medications, including immune checkpoint inhibitors (ICIs). We present the case of an 81-year-old male with a history of recurrent metastatic melanoma previously treated with nivolumab and relatlimab (Opdualag), who developed a persistent pruritic eruption following initiation of dual PD-1/LAG-3 blockade. Despite discontinuation of immunotherapy six months before dermatologic evaluation and use of multiple topical corticosteroids and oral antihistamines, symptoms persisted. A punch biopsy and direct immunofluorescence demonstrated linear IgG and C3 deposition along the basement membrane zone, consistent with BP. On initial dermatologic examination, urticarial pink plaques involved approximately 50% of the body surface area, with lesions affecting the left medial inferior chest and epigastric region. Treatment with subcutaneous dupilumab was initiated alongside clobetasol 0.05% ointment. At follow-up, the patient reported persistent activity, receiving intramuscular triamcinolone acetonide and adjunctive therapies, including hydroxyzine, hydrocortisone 2.5% cream (for groin), and triamcinolone 0.1% ointment. By the second week of treatment, new plaques continued to appear daily without subjective improvement. Objective scoring with the Bullous Pemphigoid Disease Area Index was not obtained. This case illustrates the diagnostic and therapeutic challenges in managing ICI-induced BP and highlights the early course of dupilumab therapy, which had not yet produced clinical improvement at the time of last follow-up. Continued therapy was planned, and no adverse effects were reported.