AB0826 Profile of myositis-specific antibodies in patients with polymyositis/dermatomyositis and association with clinical manifestations and outcome: experience from a tertiary referral centre
Authors: Z. Chen, X.-P. Li, X.-M. Li
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Myositis-specific antibodies (MSAs) have been found to be associated with distinct clinical phenotype and prognosis in patients with Idiopathic Inflammatory Myopathies. <h3>Objectives</h3> To assess the profile of MSAs in Chinese patients with polymyositis (PM)/dermatomyositis (DM) and explore association of antibody profile with clinical characteristics, laboratory findings and prognosis. <h3>Methods</h3> 90 patients with PM/DM were enrolled. 12 MSAs (mi-2α, mi-2β, TIF1γ, MDA5, NXP2, SAE1, Jo-1, SRP, PL-7, PL-12, EJ, OJ) were measured by immunoblotting. Associations between antibody profile and clinical manifestations, laboratory data and outcome were determined. <h3>Results</h3> The study population comprised 20 patients with PM and 70 patients with DM, in which 17 DM patients were identified as clinically amyopathic dermatomyositis (CADM). Overall, the most common MSA was anti-ARS (Jo-1/PL-7/PL-12/OJ/EJ) (41.1%), followed by anti-MDA5 (33.3%), anti-SRP (15.6%), anti-NXP2/anti-SAE1 (13.3%), anti-TIF1γ (12.2%) and anti-mi-2α/mi-2β (5.6%). Anti-MDA5 antibody was exclusively seen in DM and CADM patients and the prevalence was higher in CADM than in conventional DM (82.4% vs 30.2%, p&lt;0.001). Compared with those who were anti-MDA5 negative, patients with positive anti-MDA5 had more rapidly progressive interstitial lung disease (ILD) and Gottron sign (93.3% vs 61.7%, p&lt;0.05; 93.3% vs 38.3%, p&lt;0.001) as well as lower creatine kinase concentrations (70.0 vs 992.5 IU/L, p&lt;0.001). Anti-Jo-1 antibody was more prevalent in PM (55.0% vs 20.8%, p&lt;0.05) and patients with positive anti-Jo-1 demonstrated higher prevalence of mechanic's hands (18.2% vs 1.5%, p&lt;0.05). Anti-SRP positive patients had higher creatine kinase levels than those with negative, although there is no statistical significance (1649.5 vs 199.0 IU/L, p=0.056). Moreover, anti-TIF1γ antibody was associated with more frequent tumour (18.2% vs 0.0%, p&lt;0.01). In logistic regression analysis, anti-MDA5 [OR=9.601, 95% CI (1.940, 47.515), p&lt;0.01] was an independent risk factor for ILD. During the follow-up period (median 8 months), 13 patients died, among which 9 were anti-MDA5 positive. The survival time of anti-MDA5 positive patients was significantly less than those who were negative (3.0 vs 11.0 months, p&lt;0.01). <h3>Conclusions</h3> Anti-ARS antibodies are the most common MSAs in Chinese PM/DM patients. Anti-MDA5 is predominantly seen in patients with CADM and closely associated with rapidly progressive ILD and high mortality thus serve as a marker of poor prognosis. Anti-TIF1γ positive patients routinely screened for tumours will be of clinical significance. <h3>References</h3> [1] Clin Rev Allergy Immunol. 2017Feb;52(1):1–19. doi:10.1007/s12016–015–8510-y [2] Curr Opin Rheumatol. 2016Nov;28(6):636–44. doi:10.1097/BOR.0000000000000329 <h3>Acknowledgements</h3> We appreciate Dr Rui-Tao Liu for collecting serum samples of PM/DM patients. <h3>Disclosure of Interest</h3> None declared