(A209) Black Hairy Tongue as a Side Effect of Immune Checkpoint Inhibition - A Case Report

Introduction: Immune checkpoint inhibitors (ICI), including the PD-1 receptor inhibitor pembrolizumab, have become key therapeutic agents for various malignancies. While ICIs are known to cause immune-related adverse events, less common side effects, including black hairy tongue (BHT), have limited documentation. In this case report, we discuss a patient who developed BHT while on pembrolizumab therapy to raise awareness of this side effect.

Methods: An 82-year-old female being treated with pembrolizumab for vaginal mucosal melanoma was referred to otolaryngology clinic for black discoloration of her oral tongue. The patient was asymptomatic at presentation and did not have other risk factors for BHT including smoking or poor oral hygiene.

Results: Initial treatment with chlorhexidine mouthwash temporarily improved the discoloration, however the discoloration recurred and she also developed migrating oral ulcers and gingival bleeding related to ICI therapy. Resolution of the tongue discoloration and ulcers was achieved with further supportive care after completion of pembrolizumab therapy.

Conclusions: Black hairy tongue is a rare side effect of pembrolizumab therapy with limited documentation in the literature. The underlying mechanism may involve immune modulation affecting oral mucosal environments. Supportive care, such as oral rinses, is generally sufficient until ICI therapy is completed. As indications for ICIs expand, primary care providers, oncologists, and otolaryngologists should be vigilant in identifying and managing uncommon side effects of these medications.