Introduction: Contactin-associated protein like-2 (CASPR2)- autoantibodies are associated with distinctive syndromes 1 , such as agrypnia excitata, psychosis, neuromytonia and limbic encephalitis. All of them are highly responsive to immunotherapy. The target of these directly pathogenetic autoantibodies are surface-exposed domains of CASPR2 2 . Due to the fact of multiple variations of clinical presentations, it may be challenging to distinguish particular an autoimmune encephalitis associated with anti-neuronal autoantibodies, from primary psychiatric disorders such as psychosis. First medical treatment should be immediate immunotherapy, such as steroids, intravenous antibodies or plasma exchange given fast diagnosis of encephalitis is made. In our case the EEG showed focal slow waves with the clinical presentation of an acute psychosis which leaded to an admission to the neurology ward and further investigations. Patient and methods: A 75-years-old man was hospitalized on a psychiatric ward for psychotic symptoms characterized by psychomotor agitation, thought disorganization, persecutory delusions and auditory hallucinations with commanding voices and global insomnia. Cerebral Imaging with cMRI and cCT scan showed no acute abnormalities. EEG showed focal intermittent slow delta-theta wave activity (4-6 Hz) on the left temporal lobe, reactive to visual stimuli and provided focal cerebral dysfunction and pathology. CSF did not reveal any evidence of infection, but CASPR2- autoantibodies (1:10.000) were indentified and the diagnosis of limbic encephalitis with CASPR2-antibodies was made. Treatment with high dose dexamethasone and intravenous immunoglobulin (IVIG) was made and the clinical conditions improved. Conclusion: Fast and first medical treatment of autoimmune encephalitis should be initiated in early stages. To avoid an unnecessary delay in diagnosis and treatment, EEG, cMRI and expanded CSF examination should be performed as soon as possible to prevent severe disability in patients with limbic encephalitis with CASPR2-antibodies.