Anti-NMDA Receptor Encephalitis Related to Renal Cell Carcinoma: A Case Report

Anti-NMDA receptor (NMDAR) encephalitis is characterized by a well-defined neuropsychiatric syndrome and CSF antibodies against the GluN1 subunit of the NMDAR. 40% of cases are related to underlying tumors, the vast majority ovarian teratomas (94%). We report a case of anti-NMDAR encephalitis associated with renal cell carcinoma (RCC). A 20-year-old female presented to the ED with behavioral changes, involuntary movements, tachycardia, and alternating obtundation with agitation which progressed over 3 weeks. Involuntary movements were severe, requiring intubation and sedation for control, and were accompanied by rhabdomyolysis. Brain MRI showed bilateral mesiotemporal T2/FLAIR hyperintensities. Anti-NMDAR antibodies were present in the serum (1:640) and CSF (1:320). Malignancy screening revealed a renal mass concerning for RCC, which was confirmed upon resection. She was started on high dose IV methylprednisolone and plasmapheresis, followed by rituximab. Lack of response led to escalating immunotherapy with cyclophosphamide. Clinical course was complicated by prolonged ICU admission, prolonged sedation, severe dysautonomia and bacteremia. Improvement began 2 months after immunotherapy, and she was discharged to rehabilitation 100 days after admission with mild neuropsychiatric symptoms. Repeat malignancy screenings, including whole-body imaging and transvaginal ultrasound were consistently negative. Herein, we describe a case of definite anti-NMDAR encephalitis in the setting of newly diagnosed RCC. This case illustrates how tumors other than ovarian teratomas may act as immunological triggers, as well as the complex and prolonged symptomatic and immunosuppressive therapies required in severe presentations of anti-NMDAR encephalitis.