INTRODUCTION

Autoimmune encephalitis is a rare immune-related adverse event of PD-1 inhibitors, nivolumab and pembrolizumab. Autoimmune hypophysitis can also be seen with the use of these agents. The relationship between these two phenomena is currently unknown.

CASE REPORT

We describe a 79-year-old man with anterior scalp melanoma who received adjuvant nivolumab therapy. Sixteen weeks after the completion of nivolumab therapy, the patient presented to the hospital with altered mental status, anterograde amnesia, and symptoms of nausea and vomiting. The patient's encephalopathy was associated with confabulations. Workup identified increased CSF protein without increased cellularity, along with decreased serum cortisol and ACTH levels. This was consistent with encephalitis and central adrenal insufficiency.

MANAGEMENT AND OUTCOME

The patient had a robust clinical response to steroids, with resolution of mental status changes and normalization of blood pressure. He continues to receive maintenance steroid therapy without any further symptoms six months later.

CONCLUSIONS

We report herein a unique case of encephalopathy in the setting of nivolumab use for the treatment of melanoma. The condition resembled Korsakoff psychosis seen in the setting of alcoholism and was associated with central adrenal insufficiency. A prompt response to steroids was both diagnostic and therapeutic in our case, suggesting the resolution of autoimmune phenomena related to nivolumab.