Intrathecal synthesis of beta-2-microglobulin in multiple sclerosis and aseptic meningo-encephalitis.

Beta-2-microglobulin (beta 2m) levels were studied in the cerebrospinal fluid (CSF) and plasma of 52 patients with clinically definite multiple sclerosis (MS) and of 14 with aseptic meningo-encephalitis (AM). Reference values for beta 2m were defined in 72 subjects of different age groups with tension headache (TH). Plasma levels of beta 2m increased with age in TH controls, particularly in the older age group, while no significant age variation could be detected for CSF beta 2m. Increased levels of beta 2m were found in the CSF and plasma of AM patients and in the CSF in MS. Calculations of CSF/plasma beta 2m ratios showed higher values in AM, reflecting intrathecal beta 2m synthesis, while only borderline alterations were evident in MS. Demonstration of intrathecal production of beta 2m is an additional CSF finding that may be useful in evaluating, among others, inflammatory nervous system disorders, but it has limited importance in the study of MS patients.