Abstract
BackgroundInterpretation of rituximab efficacy for refractory idiopathic inflammatory myopathies (IIM) is hampered by the absence of a uniform definition of refractory myositis and clinical response. Therefore, rigorous criteria of refractoriness, together with a homogenous definition of clinical improvement, were used to evaluate rituximab one-year response.MethodsA retrospective cohort study including 43 IIM (15 antisynthetase syndrome, 16 dermatomyositis, 12 polymyositis) was conducted. All patients had refractory disease (inadequate response to at least two immunosuppressives/immunomodulatories and no less than three months sequentially or concomitantly glucocorticoid tapering) criteria. Clinical/laboratory improvement at one-year was based on modified International Myositis Assessment & Clinical Studies Group (IMACS) core set measures. The patients received two infusions of rituximab (1 g each) at baseline, followed by repeated dose after 6 months. Baseline immunosuppressive therapy was maintained and glucocorticoid dose was tapered according to clinical/laboratory parameters.ResultsFive patients had side effects at the first rituximab application and were excluded. Therefore, 38 out of 43 patients completed the one-year follow up. Almost 75% of the patients attained clinical and laboratory response after one-year. A significant reduction in median glucocorticoid dose (18.8 vs. 6.3 mg/day) was achieved and 42% patients were able to discontinue prednisone. In contrast, young individuals and patients with dysphagia had a tendency to be non-responders to rituximab. No severe infections were observed.ConclusionThis study provides convincing evidence that rituximab is an effective and safe therapy for refractory IIM.
Highlights
Interpretation of rituximab efficacy for refractory idiopathic inflammatory myopathies (IIM) is hampered by the absence of a uniform definition of refractory myositis and clinical response
The disease activity core set measures validated by the International Myositis Assessment & Clinical Studies Group (IMACS) [12, 13] have not been previously used to evaluate refractory IIM response to therapy
Five of the initial 43 patients were later excluded due to moderate allergic reactions to the first rituximab infusion (N = 4) or lost to follow-up (N = 1)
Summary
Interpretation of rituximab efficacy for refractory idiopathic inflammatory myopathies (IIM) is hampered by the absence of a uniform definition of refractory myositis and clinical response. Idiopathic inflammatory myopathies (IIM) constitute a heterogeneous group of chronic systemic autoimmune diseases with a high rate of morbidity and disability [1,2,3]. Based on their clinical, laboratory, histopathological and progression features, IIM can be classified as polymyositis (PM), dermatomyositis (DM), antisynthetase syndrome (ASS), inclusion body myositis, and others [2, 3]. These measures defined response as a > 20% improvement on three out of any 6 of the following core set measures: Health Assessment Questionnaire (HAQ); Manual Muscle Testing-8 (MMT-8); Physician Global Activity - Visual Analogue Scale (VAS); Patient Global Activity - VAS; serum muscle enzymes; Myositis Disease Activity Assessment Tool (MDAAT); with no more than two core set measures worsening by > 25%, which cannot include MMT
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