Paraneoplastic Encephalitis Associated with Renal Cell Carcinoma

Purpose Paraneoplastic encephalitis is autoimmune encephalitis accompanied by tumors. Renal cell carcinoma (RCC) is a kidney cancer originating from various types of renal cells and rarely has been associated with paraneoplastic neurologic manifestation. We identified a case series of paraneoplastic encephalitis-associated RCC. Methods From a prospective institutional cohort, we identified autoimmune encephalitis patients with RCC. The association between RCC and encephalitis was determined by the following criteria: (1) possible autoimmune encephalitis according to the operational autoimmune encephalitis diagnostic criteria and (2) RCC simultaneously diagnosed with neurological manifestation of encephalitis. Results A total of three patients presented encephalitis accompanied by RCC. Two patients had clear cell RCC, and one had chromophobe RCC. All patients showed limbic encephalitis with cognitive decline, memory impairment, or seizure. Brain magnetic resonance imaging showed T2 hyperintensities at the mesial temporal lobe in two patients with clear cell RCC but no remarkable findings in one patient with chromophobe RCC. While one patient who had early surgery within one month of RCC onset had a favorable response to the treatment, the other two patients showed a partial response and a detrimental result. Conclusion Paraneoplastic encephalitis associated with RCC presented as limbic encephalitis and was responsive to immunotherapy combined with tumor resection. As our cases identified, RCC should be considered as a cause of seronegative autoimmune encephalitis.