Stevens-Johnson syndrome manifesting late in the course of pembrolizumab therapy.

Pembrolizumab is a humanized antibody that targets programmed cell death receptor-1. This agent is approved for use in the treatment of several malignancies. While pruritus and papulo-erythematous rash are not uncommon with its use, severe reactions such as Stevens-Johnson syndrome/toxic epidermal necrolysis are very rare. We present herein a case of Stevens-Johnson syndrome occurring in a patient who had previously tolerated pembrolizumab without significant side effects for seven months. Prompt recognition of Stevens-Johnson syndrome/toxic epidermal necrolysis and discontinuation of the offending agent are paramount to ensure a favorable outcome.