Bullous Pemphigoid Associated With Pembrolizumab Therapy for Non-Small-Cell Lung Cancer: A Case Report

Pembrolizumab is an immune checkpoint inhibitor being increasingly used as immunotherapy for a multitude of cancers. With the increasing use of these agents, various immune-related adverse events are being recognized. Lichenoid reaction, pruritus, and eczema are well-established cutaneous side effects of pembrolizumab, but bullous pemphigoid (BP) is a rare side effect of the drug. It is difficult to establish this diagnosis because it needs a detailed history of the timeline of the evolution of symptoms and careful ruling out of other etiologies, especially other drugs. Here, we present the case of a 66-year-old male who developed BP after receiving pembrolizumab therapy for non-small-cell lung cancer. Discontinuation of pembrolizumab and the use of topical and systemic steroids led to the complete resolution of symptoms. Physicians should be aware of this potential complication and keep it on their differential diagnosis when treating patients on immune checkpoint inhibitors.