Disease stabilization with pembrolizumab for metastatic acral melanoma in the setting of autoimmune bullous pemphigoid

Background: To date, patients with pre-existing autoimmune conditions have been excluded from immunotherapy trials out of concern for severe autoimmune exacerbations. Case Presentation: We describe the first case of a patient with metastatic cKIT mutated acral melanoma, brain metastasis, and pre-existing severe autoimmune bullous pemphigoid (BP) with stable and asymptomatic disease 10 months after treatment with pembrolizumab. The patient experienced severe BP exacerbation after therapy with ipilimumab requiring systemic immune suppression, but nonetheless pembrolizumab was administered on further disease progression. Conclusions: This case suggests that pembrolizumab may confer more benefit than risk even in patients with known severe autoimmune conditions who require intermittent systemic immunosuppression.