University of Washington Seattle, Washington, United States
Disclosure(s): No financial relationships with ineligible companies to disclose
Background/Purpose: Juvenile dermatomyositis (JDM) is an inflammatory vasculopathy characterized by muscle weakness and systemic inflammation. This study aimed to investigate the clinical utility of neutrophil activation markers, specifically calprotectin (S100A8/A9) and myeloperoxidase (MPO)-DNA complexes, as potential biomarkers for muscle inflammation and predictors of long-term outcomes in JDM. Methods: Plasma levels of calprotectin and MPO-DNA were quantified using ELISA in JDM (n = 36), juvenile idiopathic arthritis (JIA, n = 13), and healthy controls (HCs, n = 21). Disease severity and muscle function were assessed using the Childhood Myositis Assessment Scale (CMAS), Physician Global Assessment (PGA), and Manual Muscle Testing 8 (MMT8). Results: JDM patients exhibited significantly higher plasma calprotectin and MPO-DNA levels as compared to HCs (p=0.0008 and p=0.0048, respectively) (Figures 1A-B). Calprotectin levels correlated with muscle function scores (CMAS r=-0.682, p=0.0002; MMT8 r=-0.59, p=0.005; and PGA muscle scores r=0.452, p=0.014) (Figure 1C). ROC analysis demonstrated that baseline calprotectin and MPO-DNA levels could distinguish active disease with high accuracy (AUC = 0.85 and 0.80, respectively) (Figure 1D). Further stratification showed that patients with elevated levels of both markers had significantly worse disease activity and muscle involvement (Figures 1E-F). Notably, higher baseline levels of these markers correlated with improved MMT8 scores over time (r=0.634, p=0.027; r=0.582, p=0.047) (Figures 2A-B), indicating a predictive role in muscle recovery. Conclusion: Calprotectin and MPO-DNA represent promising biomarkers for muscle inflammation and functional outcomes in JDM. These results suggest that neutrophil activation plays a key role in JDM pathogenesis and may provide insights into disease monitoring and treatment strategies.
