The BETPSY project will benefit to patients with rare neuroimmune syndroms such as Autoimmune Encephalitis (AE) and Paraneoplastic Neurological Syndromes (PNS) leading to a better and early diagnosis, as well as treatment improvement.Autoimmune encephalitis (AE) and paraneoplastic neurological syndromes (PNS) are rare neuroimmune syndromes with a wide range of clinical presentation but without pathognomonic clinical sign facilitating the diagnosis. Moreover, these syndromes are probably under diagnosed with only 300 patients diagnosed in 2018 out of 800 predicted. Although rare, the diagnosis of AE or PNS is essential, as despite severe neurological symptoms, patients can be cured by appropriate immunotherapy. These syndromes are characterized by the presence in the serum and cerebrospinal fluid of autoantibodies directed against neuronal targets. These autoantibodies are highly specific of AE and PNS and can be used as biomarkers of the disease.The BETPSY project will make it possible to better characterize AE and PNS patients to identify new diagnostic and prognostic biomarkers and develop new diagnostic kits. This will lead to a better and early diagnosis, as well as treatment improvement.BETPSY project has been awarded 7.3 million euros by the "Programme d'Investissement d'avenir (PIA)", and is based on a collaboration between 5 academic research teams (UCBL, HCL, ICM, CLB and INSERM), and 1 private company Euroimmun, which is specialized in the development of diagnostic kits to identify autoantibodies. This project is coordinated by Professor Jérôme Honnorat, PU-PH, head of the neuro-oncology department at the Neurological hospital of Lyon and also director of the French rare disease reference center "paraneoplastic neurological syndrome and autoimmune encephalitis" since 2007.