Pembrolizumab-Related Neuroinflammation: A Case Report and Review of the Literature

We report, to our knowledge, the first case of extralimbic pembrolizumab‐related neuroinflammation in a 71-year-old man with insidious and progressive neurologic decline during single-agent therapy for metastatic melanoma. The imaging features are nonspecific and consistent with a progressive leukoencephalopathy, for which paraneoplastic, autoimmune, and infectious encephalitis are diagnostic considerations. Recognition of this entity is important because checkpoint inhibitor treatments are increasing and permanent neurologic sequelae may be thwarted with the cessation of therapy and implementation of immunosuppression.