FRI0306 IDIOPATHIC INFLAMMATORY MYOPATHIESAND ANTISYNTHETASE SYNDROME: CONTRIBUTION OF ANTISYNTHETASE ANTIBODIES TO IMPROVE CURRENT CLASSIFICATION CRITERIA
Authors: Martín Greco, María Jesús García de Yébenes, Inmaculada Alarcón, Anahy Brandy-Garcia, Iñigo Rua-Figueroa, Estíbaliz Loza, Loreto Carmona
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> The presence of muscle weakness and anti-Jo1 anti-aminoacyl transfer RNA synthetase (ARS) autoantibodies, are evaluated in the new EULAR/ACR proposed classification criteria for adult and juvenile idiopathic inflammatory myopathies (IIM), as well as in the Solomon proposed criteria for antisynthetase syndrome (ASSD) diagnosis (1, 2). That favors an overlapping in both criteria fulfillment; however, the ASSD are not considered among the IIM subgroups classification. Anti-Jo1 ARS positivity is the highest weighted criterion in the EULAR/ACR criteria; nevertheless, other ARS were not included. Any ARS positivity is considered in Solomon's criteria. <h3>Objectives</h3> To evaluate if the detection of non-anti-Jo1 ARS could improve the EULAR/ACR criteria performance, and additionally to contribute to a better classification of the antisynthetase syndromes. <h3>Methods</h3> We performed an observational retrospective study in 2 centers. All patients with clinical suspicion of ASSD or myositis, and positive ARS in the myositis immunoblot (Euroimmun assay) were included. We assessed: 1) The rate of patients meeting EULAR/ACR and Solomon's criteria; 2) The rate of patients with anti-Jo1 and with non-anti-Jo1 ARS that fulfilled them; and 3) The rate of patients with non-anti-Jo1 ARS meeting the EULAR/ACR criteria if we assign to these antibodies the same weight as anti-Jo1 ARS. <h3>Results</h3> A total of 37 patients were included; 70.3% woman, with a mean age at the moment of the ARS detection of 51.4 (SD±14.0) years. The frequency of ARS was: anti-Jo1 (n=17), anti-PL-12 (n=8), anti-PL-7 (n=4), anti-EJ (n=4), and anti-OJ (n=4). Twenty-two of 34 patients (59.5%) met EULAR/ACR criteria and 17 (45.9%) met Solomon's criteria. Thirteen patients (35.1%) fulfilled both criteria, representing the 59.1% of those who met EULAR/ACR criteria and the 76.5% of those who met Solomon's criteria. Analyzing by antibodies, all patients with anti-Jo1 ARS (n=17) met EULAR/ACR criteria. Among the patients with non-anti-Jo1 ARS (n=20), only 5 (25%) met the criteria; however, if we gave the anti-Jo1 weight to the other ARS when applying the EULAR/ACR criteria, 19 of the 20 cases (95%) would meet them. Besides, considering the clinical features, 10 of the 20 patients with non-anti-Jo1 ARS (50%) presented clinically objectified muscle weakness, and only 4 of them met EULAR/ACR criteria; nevertheless, weighing any ARS as anti-Jo1, the other 6 cases would be reclassified as IIM. <h3>Conclusion</h3> All cases with anti-Jo1 positivity met EULAR/ACR criteria, but not those with other ARS. Nevertheless, when we applied the EULAR/ACR criteria assigning to all ARS the same weight as anti-Jo1, all except one patient fulfilled the criteria; thus, the most important result was that all patients with clinically objectified muscle weakness and non-anti-Jo1 ARS that initially did not meet the EULAR/ACR criteria could be re-classified as IIM. In this way, our results suggests that the detection of non-anti-Jo1 ARS in patients with myopathy suspicion, could increase the sensitivity of the EULAR/ACR classification criteria; and that the ASSD, when presents myositis, should be considered among the IIM classification subgroups. <h3>References</h3> [1] Lundberg IE, et al. Annals of the rheumatic diseases. 2017;76(12):1955-64. [2] Solomon J, et al. Jornal brasileiro de pneumologia. 2011;37(1):100-9. <h3>Disclosure of Interests</h3> Martín Greco: None declared, María Jesús García de Yébenes: None declared, Inmaculada Alarcón: None declared, Anahy Brandy-Garcia: None declared, Iñigo Rua-Figueroa: None declared, Estíbaliz Loza Grant/research support from: Roche, MSD, Pfizer, Abbvie, BMS, UCB, Actelion, Celgene, Grunenthal and Sanofi, Loreto Carmona Grant/research support from: Abbvie, Actelion, Astellas, BMS, Eisay, Gebro Pharma, Grünenthal, Leo Pharma, Lilly, MSD, Novartis, Pfizer, Roche, Sanofi-Aventis and UCB Pharma, Paid instructor for: Novartis