The results of routine cerebrospinal fluid tests; tests for autoimmune encephalitis-related antibodies, paraneoplastic syndrome-related antibodies, oligoclonal bands, aquaporin-4, myelin oligodendrocyte glycoprotein, glial fibrillary acidic protein, and autoantibodies; metabolic screening tests; and other screening tests were all negative. The gene discussed is AQP4; the disease is autoimmune encephalitis.