Rituximab as a glucocorticoid-sparing agent in idiopathic inflammatory myopathies: a retrospective single-center cohort study.

BACKGROUND

Idiopathic inflammatory myopathies (IIM) are essentially treated aiming to improve muscle function and extra muscular disease manifestations. Rituximab is potentially a glucocorticoid-sparing agent which was reviewed in multiple studies with small sample sizes due to the rarity of the disease. Higher statistical power can enhance the trustworthiness of alternative treatment modalities yielding the main objective of this study.

METHODS

This retrospective study was conducted at a tertiary rheumatology center. Patients were diagnosed with an idiopathic inflammatory myopathy (dermatomyositis (DM), polymyositis (PM)) and were treated with rituximab to be included in this study. Parameters of disease activity including acute phase reactants, muscle enzyme levels, and disease-specific autoantibodies were analyzed. The primary study endpoint was the improvement of the patient symptoms. The secondary endpoint was the decrease in the creatinine kinase level.

RESULTS

The study includes 26 patients (19 DM, 7 PM). The age of diagnosis was 42.04 ± 15.22 years; the follow-up duration was 64.84 ± 71.91 months. The mean corticosteroid dose decreased from 32.895 ± 24.399 to 8.44 ± 11.29 (p < 0.001). Other treatment methods were methotrexate (n = 18), intravenous immunoglobulin (IVIG) (n = 7), and cyclophosphamide (n = 2). Two patients were lost to follow-up.

CONCLUSION

Rituximab is shown to be effective in treating myositis along with corticosteroids as well as a corticosteroid-sparing agent in retrospective studies and open-label clinical trials; however, lack of statistical power should be underlined. Long-term decrease in steroid use and decrease in disease activity markers hint the effective use of rituximab as a glucocorticoid-sparing agent as well as its safety with minimal side effects. Key Points • Long-term decrease in steroid use and decrease in disease activity markers hint the effective use of rituximab as a glucocorticoid-sparing agent as well as its safety with minimal side effects.