Cerebrospinal fluid beta(2)-microglobulin in neuro-Behçet's syndrome

Paired serum and cerebrospinal fluid (CSF) specimens from 17 patients with Behçet's disease and central nervous system (CNS) involvement (neuro-Behçet's syndrome; NB) were studied for beta(2)-microglobulin (beta(2)MG) and albumin, using ELISA and single radial immunodiffusion, respectively. We also studied 29 patients with non-inflammatory neurological diseases for comparison. All of CSF beta(2)MG, serum beta(2)MG, Q albumin (an indicator of blood-brain barrier function), and CSF beta(2)MG index (an indicator of intrathecal beta(2)MG synthesis) were significantly elevated in patients with NB compared with the control patients. There were no significant differences in these parameters between 11 patients with chronic NB and six patients with acute NB. In nine patients with NB, CSF beta(2)MG and Q albumin were significantly decreased when the CNS manifestations were improved by successful treatment, whereas CSF beta(2)MG index and serum beta(2)MG were not significantly changed. The results indicate that the elevation of CSF beta(2)MG, which results from the transudation of serum beta(2)MG as well as the increased intrathecal synthesis presumably by infiltrating lymphocytes, is a good marker of CNS disease activity of NB. The data, however, also suggest that the intrathecal synthesis of beta(2)MG might not parallel to the CNS disease activity of NB, most likely due to the recovery of constitutive physiological intrathecal synthesis of beta(2)MG in spite of the withdrawal of pathological beta(2)MG synthesis at times of treatment-associated improvement.