Significance of immunoglobulins synthesis with central nervous system involvement in Neuro-Behçet's disease.

Objectives: Demyelination and immunocyte-infiltrated lesions have been found in neuro-Behçet's disease (NBD) pathology. Lacking satisfying laboratory biomarkers in NBD impedes standard clinical diagnostics. We aim to explore the ancillary indicators for NBD diagnosis unveiling its potential etiology.

Methods: 28 NBD with defined diagnosis, 29 patients with neuropsychiatric lupus erythematosus, 30 central nervous system idiopathic inflammatory demyelination diseases (CNS-IIDD), 30 CNS infections, 30 cerebrovascular diseases, and 30 noninflammatory neurological diseases (NIND) were retrospectively enrolled. Immunoglobulins (Ig) in serum and cerebral spinal fluid (CSF) were detected by immunonephelometry and myelin basic protein (MBP) by quantitative enzyme-linked immunosorbent assay.

Results: IgA index is almost twice enhanced in NBD than NIND with an accuracy of 0.8488 in differential diagnosis, the sensitivity and specificity of which were 75.00 % and 90.00 % when the cutoff was > 0.6814. The accuracy of CSF Ig and quotient of Ig all exceed 0.90 in discerning NBD with damaged and intact blood-brain barrier (BBB). Clustering analyses divided NBD into two different phenotypes: one with BBB damage has lower Ig synthesis, the other with extra-synthesis in parenchymal sites but with intact BBB. MBP index is significantly correlated with kappa (KAP) index and lambda (LAM) index (r = 0.358, 0.575, P < 0.001), hinting the NBD pathogenesis of CNS demyelination in triggering excessive intrathecal Ig productions and humoral responses.

Conclusions: IgA index acts as a potential diagnostic indicator in differentiating NBD from NIND and CNS-IIDD. Excessive immunoglobulin production induced by CNS inflammation and demyelination might be latent immunopathogenesis of NBD.