The authors report a case of bullous pemphigoid (BP) that occurred during pembrolizumab therapy in a 67-year-old male patient with advanced melanoma. Following regression of BP blisters, they reintroduced anti-PD-1 treatment. Due to the flare-up of BP, immunotherapy was discontinued again and corticosteroid was restarted. As the BP lesions regressed, interestingly, new skin metastases developed, exactly where the blisters were. One year after discontinuation of anti-PD-1 treatment, considering the significant tumor progression, pembrolizumab was restarted. This induced tumor remission, while the added low-dose corticosteroid was able to prevent the recurrence of BP. The patient carries the BP-predisposing HLA-DQB1*03:01 allele. In conclusion, anti-PD-1 rechallenge may be considered in metastatic melanoma, even if restarting anti-PD-1 has previously caused the flare-up of BP symptoms.
Keywords: HLA-DQB1*03:01; adverse reaction; bullous pemphigoid; melanoma; pembrolizumab.
Immune checkpoint inhibitors prolong the survival of patients with metastatic melanoma. Bullous pemphigoid (BP) is a rare, cutaneous, immune-related adverse event. The authors report a case of BP that occurred during pembrolizumab therapy in a 67-year-old male patient with advanced melanoma who responded to anti-PD-1 treatment with a partial response. Following the resolution of BP symptoms, pembrolizumab treatment was restarted after discontinuation of systemic corticosteroid therapy. Due to the flare-up of BP, anti-PD-1 treatment was discontinued and steroid therapy was restarted; however, skin metastases soon developed, exactly where the BP blisters were. Pembrolizumab rechallenge was successful in inducing the complete regression of skin metastases, while the added low-dose corticosteroid was able to prevent the recurrence of BP.