Background/Purpose:

Recent studies have suggested the possible benefit of the anti-CD20 agent Rituximab (RTX) in autoimmune myositis (AIM). As AIM is a rare and heterogeneous condition, no randomized controlled trial results are available to validate these findings. We present a two-center experience with the use of RTX in AIM.

Methods:

Adult patients (pts) with AIM treated with RTX between years 2005-2016 were identified by electronic medical record inquiry from two large urban multispecialty care systems in the Twin Cities, Minnesota. Charts were reviewed by two trained rheumatologists to confirm the correct diagnosis and treatment. 28 cases were identified, of them 16 pts were classified as primary idiopathic myositis (PIM) by accepted diagnostic criteria and 12 pts were classified as overlap myositis (OM) by criteria for their respective connective tissue disease (CTD) and clinically demonstrated inflammatory myositis. RTX was used for disease refractory to initial treatment, severe initial onset, and the presence of interstitial lung disease (ILD). Outcomes data for up to the first 3 RTX courses were obtained from clinical records, up to 4 months prior to each RTX and 4-6 months post RTX, and included prednisone dose, serum creatinine kinase (CK), serum C-reactive protein (CRP), forced vital capacity (FVC), and hip flexion strength (HFS). Paired sample T-tests were used for analysis.

Results:

For pts with PIM, mean age was 43 ± 16 y, 8 were female (50%), and mean disease duration was 33 ± 48 mo, with subgroups of 7 with dermatomyositis, 6 with polymyositis, and 3 with necrotizing autoimmune myopathy. For pts with OM, mean age was 53 ± 13 y, 11 were female (92%), and mean disease duration was 47 ± 54 mo, with subgroups of 7 with systemic lupus erythematosus, 2 with systemic sclerosis, 2 with Sjogren’s syndrome, and 1 with mixed CTD. The average number of non-corticosteroid medications used prior to the first RTX for pts with PIM was 2.2 ± 1.6 and for OM was 3.5 ± 1.7.

After one RTX course, pts with PIM but not OM had a significant reduction in prednisone dose from 44.38 ± 23.58 mg/day to 14.34 ± 15.27 mg/day (p=0.0002). After one RTX course, pts with PIM but not OM had a significant reduction in CRP from 25.57 ± 22.56 mg/dL to 9.61 ± 6.31 mg/dL (p=0.029). Among AIM pts with concomitant ILD, there was also a statistically significant improvement in % predicted FVC after one RTX course by 9.2 ± 8.69 % (p=0.045). There was no observed statistically significant change in CK or HFS.

Conclusion:

In 28 AIM pts treated with RTX, we observed a significant improvement in prednisone dose and serum CRP levels following the first treatment cycle for pts with PIM but not OM. There was also a modest improvement in % predicted FVC among patients with concomitant ILD, but no significant change in CK levels or HFS.

« Back to 2017 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/a-two-center-experience-with-rituximab-in-patients-with-primary-idiopathic-myositis-and-overlap-myositis-a-retrospective-observational-study/