Abstract
ObjectiveAutoantibody detection is crucial for the early diagnosis of autoimmune encephalitis (AIE) since prompt therapy can determine the disease outcome. Here, we report a single‐center 6‐year retrospective study of autoantibody testing in AIE in the Hungarian population.MethodsSerum and/or cerebrospinal fluid (CSF) autoantibody tests were performed using cell‐based indirect immunofluorescence assay for AIE diagnosis. Samples were provided by neurology clinics as part of a nationwide program. Test results were analyzed for samples received during the period from 2012 to 2018.ResultsWe tested 1,247 samples from 1,034 patients with suspected AIE. Autoantibodies were present in 60 patients (5.8% of total). The distribution of patients with different autoantibodies by age and sex was as follows: NMDAR (70%), mostly in young females, LGI1 (15%) in middle‐aged males, GABABR (12%) in elderly males, and Caspr2 (7%) in males. Long‐term follow‐up was conducted in 30 patients with repeated test requests, of which 17 remained positive, and 13 switched to negative.ConclusionWe report the most comprehensive clinical laboratory study of autoantibody testing in AIE in the Hungarian population. Our results show that the frequency of different autoantibody types in AIE corresponds to the data described in the literature.
Highlights
During the past few years, it has been recognized that there are central nervous system (CNS) disorders presenting in the form of limbic encephalitis, in which the presence of autoantibodies against the neuronal cell surface receptors such as NMDAR, GABABR, and AMPAR or synaptic proteins, LGI1 and Caspr2, has been docu‐ mented and shown to be responsible for the development of the symptoms (Dalmau, Geis, & Graus, 2017; Dalmau & Graus, 2018; Newman et al, 2016)
The autoantibodies bind to the extracellular epitopes of the neuronal cell surface receptors or their associated proteins, which can lead to alteration of the structure and function of target antigens by dif‐ ferent mechanisms
In anti‐NMDAR encephalitis, autoantibod‐ ies induce receptor cross‐linking and internalization, in anti‐LGI1 encephalitis autoantibodies interfere with protein–protein interac‐ tions, and in anti‐GABABR encephalitis autoantibodies may block the function of the target antigen (Hughes et al, 2010; Ohkawa et al, 2013)
Summary
The autoantibodies bind to the extracellular epitopes of the neuronal cell surface receptors or their associated proteins, which can lead to alteration of the structure and function of target antigens by dif‐ ferent mechanisms. In anti‐NMDAR encephalitis, autoantibod‐ ies induce receptor cross‐linking and internalization, in anti‐LGI1 encephalitis autoantibodies interfere with protein–protein interac‐ tions, and in anti‐GABABR encephalitis autoantibodies may block the function of the target antigen (Hughes et al, 2010; Ohkawa et al, 2013). Patients can have a fatal outcome in case of lack of the proper therapy. This highlights the importance of early clinical diagnosis of AIE, in which the laboratory has a crucial role by providing accurate and reproducible testing of serum and/or cerebrospinal fluid (CSF) samples for the presence of autoantibodies
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