AB1309 CLINICAL CHARACTERISTICS OF NEW-ONSET IDIOPATHIC INFLAMMATORY MYOPATHIES FOLLOWING SARS-CoV-2 INFECTION OR VACCINATION – ANALYSIS OF A CASE SERIES

Background Recent data showed that SARS-CoV-2 infection and vaccination could act as a trigger for different autoimmune diseases, including idiopathic inflammatory myopathies (IIM). Objectives The aim of this study was to describe the clinical characteristics of patients diagnosed with IIM following SARS-CoV-2 infection and vaccination in a tertiary rheumatology center. Methods We conducted a retrospective analysis on patients newly diagnosed with IIM, from 1 January 2020 to 31 December 2022, using information from the hospital database. The patients were selected according to the ICD-10 codes indicating IIM (M33.0, M33.1, M33.2, and M33.9). The cases with onset of specific IIM symptoms within 6 months after SARS-CoV-2 infection or vaccination were selected for further analysis. Clinical, biological and immunological parameters were assessed using descriptive statistics. Results A total of 58 patients newly diagnosed with IIM were identified, and in 10 (17.2 %) patients the onset was after SARS-CoV-2 infection (n = 6) or vaccination (n = 4). All patients diagnosed with IIM following vaccination (F:M=1:1, median age 46 years) received a mRNA vaccine and had the clinical onset within several days to a month after vaccination. Among IIM cases following SARS-CoV-2 infection (F:M=1:1, median age 60.5 years), the clinical onset of myopathy was variable, with a minimum of 14 days and a maximum of 6 months after infection. Myalgia, muscle weakness and elevated levels of creatinine kinase were reported in 9 patients. The average CK level was 2534.6 (3760.8) U/L, ranging from 43 to 11827 U/L. Skin lesions were present in all patients with IIM following vaccination and in 4 cases with IIM after SARS-CoV-2 infection. Mechanic’s hands and arthralgia were noted in 5 patients each. Dyspnea and interstitial lung disease (ILD) were reported in 8 cases, with severe pulmonary involvement present in 2 cases. Myocarditis was reported in 2 patients, 1 case from each group. Myositis-specific antibodies (MSAs) and myositis-associated antibodies (MAAs) were reported in 9 patients. Anti-threonyl-tRNA synthetase antibodies (anti-PL7) were present in 5 cases (3 after vaccination and 2 after infection), anti- histidyl-tRNA synthetase antibodies (anti-Jo-1) in 2 patients (in 1 associated with anti-PL7 antibodies), and anti-isoleucyl-tRNA synthetase (anti-OJ antibodies) in 1 patient. ILD was diagnosed in all anti-PL7 antibody positive patients. Conclusion Anti-PL7 antibodies are frequent in newly diagnosed IIM following SARS-CoV-2 infection or vaccination. Further studies are needed to investigate the relationship between SARS-CoV-2 infection and vaccination in the occurrence of IIM. References [1]Galeotti C, Bayry J. Autoimmune and inflammatory diseases following COVID-19. Nat Rev Rheumatol. 2020 Aug;16(8):413–4. [2]Chen Y, Xu Z, Wang P, Li XM, Shuai ZW, Ye DQ, et al. New-onset autoimmune phenomena post-COVID-19 vaccination. Immunology. 2022 Apr;165(4):386–401. Acknowledgements I have no acknowledgements to declare. Disclosure of Interests None Declared.