First-Line Rituximab in Pediatric-Onset Multiple Sclerosis: Clinical and MRI Outcomes in a Retrospective Cohort.

B-cell depletion is increasingly used in pediatric-onset multiple sclerosis (POMS), but data on rituximab as first-line chronic therapy remain limited. We retrospectively reviewed 17 children with POMS who received rituximab as their initial long-term disease-modifying therapy at a single tertiary children's hospital. Clinical data were collected from the medical record and all contrast-enhanced brain magnetic resonance images (MRIs) were re-reviewed by a neuroradiologist for standardized T2 lesion counts. Median treatment duration was 126 weeks. After rituximab became therapeutically active (≥6 months after initiation), no clinical relapses occurred. Sixteen patients (94%) achieved a clinical + MRI activity-free composite outcome (no relapses and no new/enlarging T2 or gadolinium-enhancing lesions). Total T2 lesion counts were stable or decreased in all patients compared with the post-induction baseline. Adverse events were infrequent with no serious adverse events reported. These findings provide preliminary support for rituximab as a well-tolerated, first-line high-efficacy approach in POMS and warrant larger prospective studies.