AB0628 EMERGING AUTOANTIBODIES PANEL (MYOSITIS ASSOCIATED AND MYOSITIS SPECIFIC ANTIBODIES) IN INFLAMMATORY MYOPATHIES: THE FREQUENCIES OF AND RELATIONSHIP WITH CLINICAL FEATURES
Authors: G. K. Yardimci, E. Erul, E. Bilgin, B. Farisoğullari, L. Kiliç, Z. Saribas, U. Kalyoncu, A. Akdoğan, B. Sener, Ş. A. Bilgen, O. Karadag
Journal: Annals of the Rheumatic Diseases (2020)

Background: The idiopathic inflammatory myopathies (IIM) are characterized by muscle weakness, skin disease and various internal organ involvement and they can overlap with other autoimmune diseases. Recent autoantibody panels improve understanding and management of inflammatory myopathies. Myositis specific autoantibodies including Anti-TIF-1, Anti-NXP2, Anti-MDA5, Anti-SAE1, anti-HMGCR and anti-cN1A are regarded as key biomarkers aiding the diagnosis of patients. On the other hand, myositis-associated autoantibodies (MAAs) are also found in other autoimmune rheumatic diseases. Objectives: To investigate the clinical meaning and impact of new myositis autoantibodies panel in real life data. Methods: A total of 110 subjects (77 female, 33 male) admitted to Hacettepe University Hospitals with the signs and symptoms of IIM were screened by a line immunoblot assay (EUROLINE: Autoimmune Inflammatory Myopathies16 Ag) between 2017 and 2020. Only moderate or strong reactivity results were reported as positive. Demographic, clinical, laboratory, therapeutic data and imaging features were obtained by the retrospective review of medical records. IIM patients were diagnosed by Bohan and Peter’s criteria and classified according to the EULAR/ACR classification criteria for adult and juvenile IIM and their major subgroups. Results: IIM was diagnosed in 61 patients (42.6% DM/JDM and 57.4% PM) and patients with overlap were in decreasing order, Scleroderma (n=8), RA (n=5), Sjogren (n=4), SLE (n=3), autoimmune hepatitis (n=2). Myositis-specific autoantibodies (MSAs) were found in 60%, myositis-associated autoantibodies (MAAs) in 41% of inflammatory myositis patients. The most common MSAs were anti-Jo-1 (16.4%) and anti-MDA-5 (13.1%) and the most common MAA was Ro-52 (32.7%) (Table 1). MAAs were more common in patients with polymyositis (54% vs 23% p=0.013). Twenty-one (34.4%) patients (61.0% females) had interstitial lung disease (ILD). Anti-Jo-1 (38.1%) and anti-Ro-52 (52.4%) was the most common MSA and MAA in patients with IIM and ILD. MSAs were also determined in 10 of the 49 patients who were not diagnosed with IIM. Five patients with Anti-SRP, Anti-Mi-2 alpha, Anti-Jo-1 Anti-PL7, Anti-MDA-5 autoantibodies diagnosed as connective tissue disorder, one of them also had bladder cancer. Three patients with Anti-NXP2, Anti-PM-Scl 75, Anti-Ro-52, Anti-Mi-2 beta, Anti-PL7, Anti-PL12 autoantibodies had ILD. One patient (Anti-Mi-2 alpha, Anti-NXP2 and Anti-Ku autoantibodies positive) had viral myositis and one patient (Anti-Mi-2 alpha, Anti-Ro-52 autoantibodies positive) had inflammatory polyneuropathy. Conclusion: Our study revealed relationship of anti-Jo-1 and anti-Ro-52 but not anti-MDA-5 in ILD-inflammatory myopathies. Even though new autoantibodies panel give opportunity to a closer look for inflammatory myopathies, larger series of patients should be evaluated to determine the association of specific antibodies in the differential diagnosis and prediction of outcome of IIM. MSA positivity in non-IIM diagnosed patients should be monitored to determine whether this positivity is related to a future disease development. Disclosure of Interests: Gözde Kübra Yardimci: None declared, Enes Erul: None declared, Emre Bilgin: None declared, Bayram Farisoğullari: None declared, Levent Kiliç: None declared, Zeynep Saribas: None declared, Umut Kalyoncu Consultant of: Abbvie, Amgen, Janssen, Lilly, Novartis, UCB, Ali Akdoğan: None declared, Burcin Sener: None declared, Şule Apraş Bilgen: None declared, Omer Karadag: None declared