P.191 - Rituximab for the treatment of anti-HMGCR necrotizing autoimmune myopathy

Abstract

The effectiveness of rituximab in refractory myositis has been suggested by case reports and case series. Recently, anti-HMGCR, a new autoantibody associated with necrotizing autoimmune myopathy and related to statin exposure was discovered. Our objective was to address the effectiveness of rituximab in the subgroup of anti-HMGCR necrotizing autoimmune myopathy. We identified 4 patients with anti-HMGCR necrotizing autoimmune myopathy that were treated with rituximab. Medical records were reviewed to assess their clinical presentation, muscle testing, serum CK levels, corticosteroid doses and associated immunosuppressant agents while receiving rituximab, and their evolution at last follow-up. Only one patient had previous statin exposure. Two patients had a slowly-progressive dystrophic-like presentation over 20 years. All patients had a relapsing disease and needed multiple therapy trials and combination to maintain remission. Two patients were resistant to rituximab and clearly IVIg-dependent, requiring long-term treatment with IVIg to maintain remission. One patient had a thrombotic event while on IVIg and was successfully switched to rituximab. Another patient experienced a biological flare with an isolated CK rise following IVIg discontinuation yet subsequent slowly-progressive CK lowering with rituximab re-infusion and introduction of methotrexate. At last follow-up all patients were in clinical remission. Two of them were still on IVIg with low-dose prednisone +/− azathioprine. Two patients were adequately controlled with rituximab and low-dose prednisone +/− methotrexate. Our patients with anti-HMGCR necrotizing autoimmune myopathy had a refractory disease with multiple relapses. Larger prospective trials are needed to confirm potential efficacy of rituximab in this subgroup of patients.