Background Antisynthetase syndrome (ASS) is an idiopathic inflammatory myopathy characterised by the presence of anti-Jo-1 antibodies. Patients usually present with myositis, interstitial lung diseases, and arthritis. Corticosteroid therapy is the first line treatment. With regard to immunosuppressive use, no consensus has been reached. Rituximab has been reported to be successful in treatment of refractory ASS in small case series

Objectives We report our experience of using rituximab in refractory ASS by describing the outcome and follow up of 3 cases

Methods The case notes of 3 patients (2 males and 1 female; ages: 50, 42, and 54 years), diagnosed with ASS based on positive anti-Jo1 antibodies and muscle biopsy, were analyzed retrospectively. Treatment with several conventional therapeutic agents was tried sequentially over a mean period of 10 months without sustained remission (see Figs. 1, 2 and 3). In view of the refractory nature of their disease, a decision to commence rituximab was made (1000 mg IV, twice, with a 2-week interval). The available follow up periods for the 3 patients are 36 months in 2 patients, and 67 months in 1 patient. Response to treatment was assessed by improvement in muscle weakness & creatinine kinase (CK) levels

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Results Response to treatment was observed after a period of 4-5 months following treatment with rituximab. This manifested as improvement in symptoms (muscle weakness, joint pain and shortness of breath), & CK levels (see Figs. 1, 2, and 3). In the first patient (Fig. 1) the improvement following the initial treatment with rituximab was sustained for almost 3 years before he required retreatment with rituximab for relapses (relapsed 4 times afterwards over a period of 32 months, with an average of 11 months between relapses). Retreatment with rituximab in the second patient (Fig. 2) who relapsed at 8 and 18 months following the initial treatment resulted in remission 4-5 months later, and eventually he came off immunosupressive therapy. Retreatment with rituximab in the third patient (Fig. 3) who relapsed at 9 months following initial treatment resulted in remission 4-5 months later. She remained well and continued to receive rituximab prophylactically 6-monthly. The 3 patients have been successfully weaned off the higher dose of prednisolone they used to be on prior to treatment with rituximab; the first patient is currently maintained on prednisolone alone (10 mg daily); the second patient was weaned off prednisolone successfully and is currently on no treatment; while the third is maintained on prednisolone 5 mg daily plus methotrexate 25 mg weekly

Conclusions This small retrospective case series indicates a beneficial effect of rituximab in ASS refractory to conventional treatment, in keeping with other case series^1,2. However the response to treatment may take several months. The relapses at an average of 10 months following initial treatment with rituximab coincide with the timing of repopulation. The optimal timing of retreatment and whether prophylactic retreatment with rituximab at time of repopulation should be considered, remain to be defined.

References

1. Martha Sem et al. Rituximab treatment of the anti-synthetase syndrome - a retrospective case series. Rheumatology (2009) 48 (8): 968-971.

2. Elien A. M. Mahler et al. Rituximab treatment in patients with refractory inflammatory myopathies. Rheumatology (2011) doi: 10.1093/rheumatology/ker088

Disclosure of Interest None declared

DOI 10.1136/annrheumdis-2014-eular.1878