Bullous Pemphigoid Associated with Anti-programmed Cell Death Protein 1 and Anti-programmed Cell Death Ligand 1 Therapy: A Review of the Literature

Bullous pemphigoid constitutes a rare dermatological immune-related adverse event of programmed cell death protein 1 (PD-1)/programmed cell death ligand 1 (PD-L1) inhibitors. Herein, we review all published cases of anti-PD-1/PD-L1 related bullous pemphigoid and discuss current knowledge on this condition. Clinical and diagnostic findings were found to resemble those of classic bullous pemphigoid. A delayed onset of bullous pemphigoid after commencement of immunotherapy as well as a frequent precendence of a refractory pruritic eruption prior to blister development was oberved, both posing diagnostic challenges. In addition to topical and systemic treatment, most patients required either discontinuation or permanent interruption of immunotherapy. Assessment of tumour outcome did not reveal improved survival in patients developing bullous pemphigoid during immunotherapy, as suggested for other types of skin toxicity, including vitiligo. Better understanding of the pathogenetic mechanism and prognostic implications of this increasingly-reported adverse event is essential in order to establish optimal diagnostic and therapeutic management of these patients.