Immunoglobulin-G dynamics and relation to antibiotic prescriptions in multiple sclerosis patients treated with rituximab: a real-world cohort.

BACKGROUND

Rituximab, a B-cell-depleting therapy widely used for multiple sclerosis (MS), is associated with a progressive decline in immunoglobulin G (IgG) levels, raising concerns regarding infection risk. This study evaluates IgG dynamics and antibiotic use in a real-world MS cohort.

METHODS

A retrospective cohort study was conducted on MS patients treated with Rituximab over a 10-year period. Patients included had at least two infusions and a follow-up of ≥6 months after the last infusion. IgG levels and antibiotic prescriptions were registered longitudinally.

RESULTS

The study included 213 patients (72% female, mean age 40.1 ± 10.6 years). Mean IgG decreased from 11.5 ± 2.4 g/L at baseline to 9.0 ± 1.7 g/L after five years, with an average decline of 0.35 g/L/year (95% CI 0.25-0.44; p < 0.001). Hypogammaglobulinemia (<6.7 g/L) occurred in 7.5% of patients. Cumulative rituximab dose was a significant predictor of lower IgG (p < 0.001). Antibiotic prescriptions were recorded in 62% of patients (mean 2.5 per patient), most commonly for urinary (29%) and respiratory (17%) tract infections. In multivariable analysis, lower IgG levels did not significantly predict the risk of antibiotic prescription.

CONCLUSION

Rituximab treatment resulted in a significant, dose-dependent IgG decline. However, this decline was not associated with an increased risk of antibiotic-treated infections, suggesting a dissociation between total IgG levels and functional immune competence in this cohort. These findings support continued use of rituximab with vigilant monitoring, though dose adjustments may be warranted for patients with rapidly decreasing IgG.