Introduction Anti-neuronal antibodies (ANA) are found in paraneoplastic neurological syndrome and autoimmune encephalitis patients. Our aim was to analyze prognostic factors related with ANA seropositivity. Methods Twenty-seven consecutive ANA seropositive patients were included in the study. ANA were detected by immunofluorescent staining, immunoblot and cell-based assay methods. All patients were followed with a standard treatment protocol. Clinical syndromes, tumor types, modified Rankin scores, cranial MRI and oligoclonal band (OCB) findings were recorded. Cases were divided into subgroups due to clinical-laboratory features and ANA types. Prevalence of good prognosis, response to treatment and survival were compared among these subgroups. Results Patients showed antibodies to N-methyl-D-aspartate receptor (NMDAR) (6 cases), Hu (6 cases), Ma2 (5 cases), glutamic acid decarboxylase (GAD) (3 cases), Yo (3 cases), amphiphysin (1 case), gamma-amino butyric acid B receptor (GABABR) (1 case), Ri (1 case) and Zic4 (1 case). Associated neurological syndromes were limbic encephalitis (8 cases), subacute cerebellar degeneration (7 cases), brainstem encephalitis (5 cases), subacute sensory neuronopathy (4 cases), stiff-person syndrome (2 cases) and opsoclonus-myoclonus (1 case). A tumor (ductal breast, small cell lung cancer) was detected in six cases at first admission. Six patients died in an average follow-up time of 1.0±1.5 years. Detection of antibodies to extracellular or synaptic target antigens, but not presence of tumor, cranial MRI lesions or OCB, was associated with good prognosis and response to treatment. Conclusion NMDAR, Hu and Ma2-antibodies were the most prevalent ANA in this first antibody screening study in a Turkish cohort. Antibody type was determined to be the foremost prognostic factor in ANA seropositive cases.
