Elevated sST2 associates with cardiac involvement and declines after treatment in newly diagnosed patients with idiopathic inflammatory myopathies

Abstract Objective Cardiac involvement (CI) is a major determinant of poor prognosis in idiopathic inflammatory myopathies (IIM). Soluble suppression of tumorigenicity 2 (sST2) is a biomarker linked to cardiac inflammation and remodelling, but its role has scarcely been explored in IIM. We aimed to investigate the levels of sST2 and its longitudinal profile in patients with IIM and CI. Methods Serum sST2 levels were measured longitudinally over the course of two years in 34 patients with newly diagnosed IIM and in 109 patients with established IIM from a cross-sectional cohort, as well as in age and gender matched healthy controls (HC) and in patients with rheumatoid arthritis (RA). CI was assessed using cardiac magnetic resonance (CMR) in newly diagnosed IIM patients. Associations between sST2 and clinical parameters were analyzed. Results Patients with newly diagnosed IIM exhibited significantly higher sST2 levels at diagnosis compared to HC ( P < 0.0001) and patients with established IIM ( P < 0.0001). sST2 levels were highest at diagnosis, decreased significantly by 6 months, and remained lower during follow-up. sST2 levels were positively associated with cardiac troponin I and N-terminal pro-brain natriuretic peptide ( P = 0.0001 and P = 0.0001, respectively). Importantly, IIM patients with active CMR-verified CI exhibited significantly higher sST2 levels than those without ongoing CI. In contrast, patients with established IIM had sST2 levels comparable to HC and RA patients. Conclusion sST2 is elevated in early IIM and closely associated with cardiac biomarkers and CMR-verified cardiac inflammation. Its dynamic decline with treatment suggests potential utility as a biomarker for early detection and monitoring of CI in IIM.