Prognostic role of intrathecal IgM synthesis in multiple sclerosis: Results from a clinical series

Background: There is emerging evidence that intrathecal IgM synthesis (ITMS) is a risk factor for conversion to clinically defined multiple sclerosis (CDMS) in clinically isolated syndrome (CIS) patients. Objectives: The objective of this study is to verify the prognostic role of ITMS as a risk factor for the second clinical attack in patients after the first demyelinating event. Methods: Monocentric observational study performed on prospectively acquired clinical data and retrospective evaluation of magnetic resonance imaging (MRI) data. ITMS was assessed according to Reiber's non-linear function. We compared time to the second attack by using Kaplan-Meier curves and performed adjustment by Cox regression analysis. Results: Demographics and clinical data were collected prospectively in a cohort of 68 patients. ITMS occurred in 40% (27/68) of patients who had a higher T1-hypointense lesion load at brain MRI (p = 0.041). In multivariate Cox regression analysis (adjusted for age, sex, baseline Expanded Disability Status Scale, IgG oligoclonal bands and disease-modifying treatment exposure), relapsing-remitting multiple sclerosis (MS) patients with ITMS were at higher risk to experience a second clinical attack (adjusted hazard ratio (aHR) = 6.3, 95% confidence interval (CI) = 2.1-18.4, p = 0.001). Conclusion: Together with previous studies, our findings support the role of ITMS as a prognostic biomarker in MS.