Abstract
INTRODUCTION: Central nervous system demyelination caused by immune checkpoint inhibitors is a very rare condition. CASE PRESENTATION: A 65-year-old man who received nivolumab for renal cell carcinoma developed abnormal behavior, such as disagreeable speech and sudden anger. Brain-enhanced magnetic resonance imaging revealed multiple lesions with partial contrast effects in the cerebral white matter. We tentatively diagnosed demyelination caused by nivolumab, and performed steroid pulse therapy twice. After that, his symptoms improved. For the next 2 years, his symptoms did not recur, nor did his cancer progress. CONCLUSION: Demyelination caused by immune checkpoint inhibitors can be fatal and requires early diagnosis and treatment.