Pembrolizumab-Induced CNS Vasculitis Neurologic Adverse Events Due to Checkpoint Inhibitors

Immune checkpoint inhibitors (ICIs) are used in solid malignant tumors and associated metastasis therapy. Pembrolizumab is a humanized monoclonal antibody that binds to lymphocyte programmed cell death protein 1 (PD-1) receptors, enhancing immune surveillance against tumor cells.(1) Immune-mediated neurologic adverse events (AEs) related to ICIs have been reported, including vasculitis involving the central and peripheral nervous system. We report a rare case of presumed severe multifocal large/medium intracranial vessel vasculitis and related diagnostic challenges in a pembrolizumab-treated lung cancer patient.