Clinical heterogeneity and prognostic factors of anti-synthetase syndrome: a multi-centred retrospective cohort study

Objective Anti-synthetase syndrome (ASyS) patients have heterogeneous clinical manifestations with different initial presentations, complications and outcomes. This study aimed to assess the clinical characteristics and complications in patients with ASyS, and to identify factors that were associated with the survival of ASyS patients.Methods This was a retrospective multicentre longitudinal study. Patients fulfilling either Connor's criteria or Solomon's criteria for ASyS were recruited. Electronic health records were reviewed until October 2022. Multivariate Cox regression analysis was used to determine the independent prognostic factors. Auto-antibodies were checked by commercial immunoassays.Results A total of 205 patients (anti-Jo1 49.3%, anti-PL7 19.0%, anti-EJ 11.2%, anti-PL12 10.2% and anti-OJ 3.4%) were included. The median follow-up time was 4 years. The time from symptoms onset to diagnosis was significantly longer for non-anti-Jo1 patients (median 5 vs 3 months). Common initial presentations included myositis (56.1%), arthritis (54.6%) and interstitial lung disease (ILD) (54.1%). Patients with anti-Jo1 had significantly higher muscle enzyme levels and more arthritis. All patients with anti-EJ would develop ILD on follow-up and malignancy was noted in 28.6% of the anti-OJ positive patients; 15.6% of the patients died and pulmonary diseases (ILD or pneumonia) were the major causes. Age at diagnosis, malignancy and rapidly progressive ILD were independently associated with mortality, while joint manifestation was a protective factor.Conclusion In view of the heterogeneity of clinical presentation of ASyS, a high index of suspicion and early checking of specific autoantibodies might help prompt diagnosis of ASyS and detection of related complications.