The prevalence and clinical usefulness of anti-NXP-2 autoantibodies in patients with idiopathic inflammatory myopathies / 中华风湿病学杂志

ABSTRACT

Objective To determine the sera levels of anti-nuclear matrix protein (NXP)-2 autoantibodies and their clinical associations in patients with idiopathic inflammatory myopathies (IIM).Methods Sera from 198 Chinese patients with IIM including 15 juvenile dermatomyositis (JDM),133 dermatomyositis (DM) and 50 polymyositis (PM),other connective tissue diseases (CTDs) including 70 systemic lupus erythematosus,60 rheumatoid arthritis,15 systemic sclerosis,46 primary Sj(o)gren syndrome,10 mixed connective tissue disease and 60 healthy controls were measured by enzyme linked immunosorbent assay.The anti-NXP-2 antibodies were detected.The positive sera were further examined by immunoprecipitation assays.Statistical analyses were performed using student's t test or Mann-Wittney U test and x2 test.Results The positive rate of sera anti-NXP-2 autoantibodies in patients with IIM was 5.1％ (10/198),20.0％ (3/15) in patients with JDM,3.7％ (5/133) in patients with dermatomyositis,and 4.0％(2/50) in patients with polym-yositis.There was statistical significant difference in anti-NXP-2-positive rates between JDM,DM and PM (P＜0.05).However,the autoantibody did not present in patients with other CTDs as well as healthy controls.The anti-NXP-2-positive patients had significantly younger age [(33±20) vs (45±17) years old (t=-2.09,P＜0.05)] and higher incidence of calcinosis [30.0％(3/10) vs 2.6％(15/188)] compared with the anti-NXP-2-negativepatients (x2=0.7,P＜0.01).There were no statistical difference between the two groups in gender,disease duration,arthritis,rash,dysphagia,myasthenia,conccurrence with interstitial lung disease and cancer.In follow-up assessment,among the three JDM patients with anti-NXP-2 autoantibodies,one of them who died 10 months later had increased serum level of anti-NXP-2 autoantibody,extensive subcutaneous calcinosis,severe myasthenia and rapid progress.Conclusion This is the first report of the serum levels of anti-NXP-2 antibodies in Chinese patients with IIM and other CTDs.We find that anti-NXP-2 antibodies only exist in patients with IIM and are associated with early and calcinosis.