Rituximab in stiff-person syndrome with glutamic acid decarboxylase 65 autoantibody: a systematic review

Background: Stiff-person syndrome (SPS) is a rare autoimmune neurological disorder characterized by muscle rigidity and painful spasms, predominantly affecting young women. It is often associated with high titers of anti-glutamic acid decarboxylase (GAD) 65 antibodies. Current treatments for SPS include symptomatic therapies and immunomodulatory approaches, but there is a need for more effective therapies because many patients show incomplete responses and disease progression. Methods: The systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, with a literature search of PubMed, Web of Knowledge, Google Scholar, and Science Direct. Studies evaluating efficacy, safety, dosage, and impact on concomitant treatments of Rituximab (RTX) in SPS were selected. Data on anti-GAD titers were also analyzed. Results: Fourteen studies published between July 2005 and October 2022 were selected. The studies included 30 SPS patients treated with RTX. Data were heterogeneous regarding dosage, administration schedule, and patient assessment. RTX was generally well-tolerated, with rare side effects, including infusion reactions or infections. Significant clinical improvement occurred in most patients, with a small proportion achieving complete remission. Anti-GAD antibody titers decreased in some studies, with no consistent correlation with clinical outcomes. Conclusions: Evidence supporting the efficacy of RTX in SPS is limited by the small sample sizes of the included studies and the variability in treatment protocols. However, RTX has shown efficacy for clinical improvement. Correlation with anti-GAD titers remains still unclear. Further randomized controlled trials are needed to confirm RTX as an established treatment for SPS.