The effect of Rituximab on B cells in pediatric autoimmune rheumatic diseases.

OBJECTIVE

This study examines how demographic factors and disease conditions affect B-cell depletion and regeneration after Rituximab (RTX) infusion in pediatric patients with rheumatic conditions.

METHODS

We retrospectively reviewed 27 patients approved by the Institutional Review Board, all of whom received at least one RTX infusion, analyzing 99 lymphocyte subunits. Inclusion: patients under 18 at their first RTX infusion, diagnosed with pediatric rheumatologist-confirmed autoimmune diseases. B-cell depletion was defined as a CD19 positive B Cells (CD19+) count below 10 cells/μL, assessed at 6- and 12-months post-RTX infusion. Complete regeneration was defined as CD19+ ≥170 cells/μL using adolescent norms.

RESULTS

Most patients had connective tissue disorders (CTD); Systemic Lupus Erythematosus, Sjögren's Disease, Systemic Sclerosis; n=17; 63%), followed by vasculitis (n=5; 18.5%), juvenile dermatomyositis (n=4; 14.8%), and miscellaneous conditions (n=1; 3.7%). Among patients with CTD, 4 out of 12 (33%) had B-cell depletion at 6 months. At 12 months, 3 out of 6 (50%) achieved CD19+ counts ≥10 cells/μL, while 5 out of 6 (83%) did not reach normal levels of CD19+ (≥170 cells/μL). No significant correlation existed between immunosuppressants (mycophenolate mofetil, methotrexate, azathioprine, cyclosporine, cyclophosphamide) and CD19+≥10 cells/μL at 6 or 12 months. However, hydroxychloroquine significantly differed for persistent depletion at 12 months.

CONCLUSION

This study demonstrates that demographic factors and disease conditions influence B-cell depletion and regeneration in pediatric patients treated with RTX for rheumatic conditions. The findings highlight the variability in response to RTX and suggest that factors such as hydroxychloroquine use may impact long-term B-cell levels.