Case Report: A Rare Case of Pembrolizumab-Induced Bullous Pemphigoid.

The programmed cell death protein 1 inhibitor pembrolizumab, an immune checkpoint inhibitor, has subsequently been approved for the treatment of a wide variety of malignant tumors. Compared with conventional chemotherapy, immunotherapy is associated with a unique set of immune reactions, known collectively as immune-related adverse events. Although often mild, dermatologic toxicity can occasionally be high grade and potentially life-threatening. Here we describe a rare case of bullous pemphigoid (BP) associated with pembrolizumab. A 79-year-old male patient presented with scattered erythema, papules, blisters, and pruritus after pembrolizumab treatment. Then, the rash gradually aggravated and spread to the whole body. The extensive edematous erythema, blisters, bullae, and blood blisters were loose and easy to rupture, forming an erosive surface and with pruritus and obvious pain. The hemidesmosomal protein BP180 (type XVII collagen) was detectable in the serum, and the histological examination diagnosis was bullous pemphigoid. After 10 days of glucocorticoid (methylprednisolone, iv, 80 mg/day) treatment, new blister formation ceased. We need to increase the awareness on and facilitate the earlier identification of the cutaneous adverse effects of BP with immunotherapy so that treat can begin early in order to limit the duration and severity of toxicity.