Abstract
Posterior reversible encephalopathy syndrome (PRES) is a neurologic condition with a constellation of symptoms, including altered mentation, headaches, and often seizures. Immunosuppressive therapies and, more recently, immunotherapy have been identified as risk factors for PRES. We describe the first documented case of PRES associated with a combination of pembrolizumab and cetuximab therapy. This case presentation aims to highlight a rare but potential adverse effect associated with immunotherapy. Awareness of this association and early recognition of symptoms can lead to prompt management and resolution of PRES. Further research is needed to elucidate the mechanisms and risk factors contributing to PRES.