Abstract
A 91-year-old man was on his seventh course of pembrolizumab for recurrence of right renal pelvic cancer. On the 8th day of treatment, he was admitted to the hospital with idiopathic fever and malaise. On the 12th day, the patient experienced tonic convulsions and exhibited an impaired consciousness. Based on cerebrospinal fluid examination and the course of the disease, we diagnosed him with autoimmune meningoencephalitis as an immune-related adverse event triggered by pembrolizumab. We administered steroids, which restored the patient's consciousness. When he died of debility two months later, a pathological specimen was obtained, confirming the diagnosis of autoimmune meningoencephalitis.