Abstract:Objective To explore the clinical characteristics of leucine-rich glioma inactivation 1 protein (LGi1) antibody-associated encephalitis and the time of serum antibody turning negative. Methods A 52-year-old female patient presented with paroxysmal involuntary movement in left upper limb and face for 2.5 months and intermittent convulsions,unconsciousness and fever for 1 week.Nervous system examination found neck rigidity and positive bilateral kerning sign.Serum anti-LGi1 antibody was positive (1∶100).After being diagnosed as anti-LGi1 antibody related encephalitis,the patient was given a comprehensive treatment including hormone,gamma globulin and levetiracetam.She was hospitalized for 14 days and followed up for 12 months. Results One month after discharge,the patient was completely relieved of her clinical symptoms,but with still positive serum LGi1 antibody (1[DK]∶100).At 3,6 and 12 months after discharge,the clinical symptoms did not recur,and all serum LGi1 antibodies were negative. Conclusion In the patient with LGi1 antibody encephalitis,positive serum LGi1 antibody can turn negative.The time of clinical symptoms alleviating is not synchronized with the time of negative antibody transformation.