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Neutrophil activation in juvenile dermatomyositis: associations with muscle function and disease progression

Year: 2025

Type: article

Abstract: BACKGROUND: 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 muscle outcomes in JDM. FINDINGS: 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). JDM patients exhibited significantly higher plasma calprotectin and MPO-DNA levels as compared to HCs (p = 0.0008 and p = 0.0048, respectively). 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). Patients with elevated levels of both calprotectin and MPO-DNA tended to have greater disease activity and muscle involvement. Exploratory ROC analysis suggested that baseline calprotectin and MPO-DNA levels may help distinguish active disease. 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), suggesting an association with greater subsequent improvement in muscle strength. CONCLUSIONS: These findings highlight calprotectin and MPO-DNA as potential biomarkers for JDM muscle inflammation and functional outcomes. These results suggest that neutrophil activation plays a key role in JDM pathogenesis and may provide insights into disease monitoring and treatment strategies.

Source: Pediatric Rheumatology

DOI: 10.1186/s12969-025-01152-w