Clinical features, diagnosis, and treatment of pembrolizumab induced autoimmune encephalitis

Pembrolizumab has shown links to autoimmune encephalitis (AE), yet the exact clinical characteristics remain unclear. This study examines the clinical features of pembrolizumab-induced AE to enhance diagnostic accuracy and therapeutic strategies. Reports on pembrolizumab-induced AE were gathered via a searchable database, culminating on November 30, 2024. The median age at onset among the 34 patients was 68 years (range 47-82), with males constituting 67.6%. The average onset period for AE was 6 months (range 0.3-25) after the initial dose, with an average of 6 cycles (range 1-17). Commonly reported symptoms included confusion (38.2%), fever (35.3%), and decreased consciousness (32.4%). Cerebrospinal fluid analysis revealed elevated protein (55.9%), leukocytosis (70.6%), and normal blood glucose levels (38.2%). Antineuronal antibodies were found to be negative in 41.2% of cases and positive in 35.3%. Magnetic resonance imaging indicated T2/FLAIR hypersignal in 32.4% of cases, while the electroencephalogram revealed slow waves (11.8%) and diffuse slowing (11.8%). Following treatment with steroids, intravenous immunoglobulin, and plasmapheresis, 82.4% of patients experienced symptom improvement or recovery, though 5.9% succumbed to AE. Oncologists must consider the risk of AE when prescribing pembrolizumab. Early diagnosis and intervention for AE are crucial. Further research is needed to define the optimal treatment approach.