Atezolizumab-induced encephalitis in a patient with metastatic breast cancer: a case report and review of neurological adverse events associated with checkpoint inhibitors.

Immune-mediated encephalitis as an adverse event due to checkpoint inhibitors is very rare. We describe herein the case of a 38-year-old woman with metastatic triple-negative breast cancer who developed seizures and somnolence twelve days after receiving the first dose of Atezolizumab. Work up ruled out all infectious etiologies, and the patient was eventually diagnosed with immune-mediated meningoencephalitis. Symptoms recovered with a high-dose of steroids, and she was found to have an excellent response on follow-up imaging, which raised the question of whether a relationship exists between the occurrence, and severity of the adverse event and the response to treatment. Only a few other cases of atezolizumab-related encephalitis have been published. Early recognition and treatment are crucial; the reason why we are describing this case along with a review of the literature and a review on all the neurological immune-related adverse events due to the different checkpoint inhibitors.