Pembrolizumab-induced encephalitis in a patient with renal cell carcinoma post nephrectomy: A case report.

A new category of immune-related adverse effects has been identified due to increasing use of immune checkpoint inhibitor therapy to treat solid organ cancers. Pembrolizumab approved for renal cell carcinoma also has neurological immune-related adverse effects causing long-term morbidity. We here present a case of renal cell carcinoma post nephrectomy with suspected pembrolizumab (anti-PD-1)-induced encephalitis presenting as light headedness and dizziness treated with high dose of corticosteroid and intravenous immunoglobulin. Lumbar puncture was performed which showed elevated protein, nucleated cells with lymphocyte predominant, suggestive of chemical meningitis. Scans were found to be normal while electroencephalogram showed diffuse cerebral dysfunction indicating encephalopathy. The patient was under pembrolizumab treatment so encephalitis was suspected. Clinical attention is necessary when patients receiving immune checkpoint inhibitors appear with new neurological symptoms to prevent long-term morbidity or even possible mortality.