Coexistence of oral mucous membrane pemphigoid and lichenoid drug reaction: a case of toripalimab-triggered and pembrolizumab-aggravated oral adverse events.

Toripalimab and pembrolizumab belong to anti-programmed death receptor-1 monoclonal antibodies for the treatment of various cancers. Anti-programmed death receptor-1 therapy can cause mucocutaneous adverse events. Here, we report the first case, to our knowledge, of oral mucous membrane pemphigoid and lichenoid reaction triggered by toripalimab and aggravated by switching to pembrolizumab. Mucous membrane pemphigoid was a definite diagnosis, whereas lichenoid reaction was a clinical diagnosis without pathologic evidence. Although discontinuation of the culprit drugs achieved clinical resolution in most reported cases, multiple studies demonstrated statistically significant associations between the development of dermatologic adverse events and superior clinical outcomes. Thus, more studies are needed to find satisfactory measures in terms of both cancer control and avoidance of severe adverse events.