Serum growth differentiation factor-15 and clinical domain involvement in idiopathic inflammatory myopathies: a pilot study

Objective Idiopathic inflammatory myopathies (IIMs) are systemic autoimmune disorders with diverse clinical manifestations. Growth differentiation factor-15 (GDF-15) is a stress-responsive cytokine whose clinical associations in IIMs remain incompletely characterized. We examined serum GDF-15 and its relationships with clinical and laboratory features in IIMs. Methods This single-center cross-sectional pilot study included 37 patients with IIMs and 25 healthy controls. Between-group differences were assessed by the Mann–Whitney U test and age- and sex-adjusted linear regression of log-transformed GDF-15. Within the IIM group, associations were assessed using Spearman correlations. The principal analysis examined the association between GDF-15 and an exploratory count of involved cutaneous, bulbar, pulmonary, and cardiac domains using partial Spearman correlation adjusted for age, body mass index, and estimated glomerular filtration rate (eGFR). Results Serum GDF-15 was higher in patients with IIMs than in controls (median [IQR], 1650 [1110–2739] vs. 544 [344–1006] pg/mL; p < 0.001; adjusted geometric mean ratio, 2.56; 95% CI, 1.93–3.38; p < 0.001). GDF-15 was associated with a greater number of clinical domains involved (ρ = 0.451, p = 0.005); the adjusted partial correlation was 0.408 (95% CI, 0.143–0.662; p = 0.017). No statistically significant correlations were detected with creatine kinase or the Medical Research Council sum score. Conclusion Serum GDF-15 was associated with an exploratory count of affected clinical domains in adults with IIMs.