Association of NXP2 autoantibodies with a more severe clinical phenotype of juvenile dermatomyositis

Abstract

Objective Myositis specific autoantibodies (MSAs) correlate with a distinct clinical phenotype of juvenile dermatomyositis (JDM). This study aims to compare the clinical features of JDM patients with positive anti-NXP2, anti-MDA5 and anti-TIF1γ autoantibodies, and differences in juvenile (JDM) and adult dermatomyositis. Methods This study included 18 NXP2+ JDM patients, 12 MDA5+ JDM patients, 12 TIF1γ+ JDM patients, and 20 NXP2+ adult DM patients. Repeated measures analysis was performed to track longitudinal changes in creatine kinase (CK) levels, Childhood Myositis Assessment Scale (CMAS) scores, and IL-10/γ-interferon ratios. Kaplan-Meier survival and Cox regression analysed relapse rates and recurrence factors. Results NXP2+ JDM patients exhibited significantly elevated serum creatine kinase levels compared to MDA5+ JDM (3792 vs. 180; p<0.001), adult NXP2+DM (3792 vs. 437.5; p=0.003), and TIF1-γ+ JDM (3792 vs. 189; p<0.001). Concurrently, NXP2+ JDM patients also showed lower CMAS scores compared to MDA5+ (31.33 vs. 43.25; p<0.001) and TIF1-γ+ JDM groups (31.33 vs. 42.67; p=0.004). The NXP2+ JDM patients presented with a high frequency of macrophage activation syndrome (MAS), myocardial damage, dysphagia, and calcinosis. Repeated measures analysis showed that NXP2+ JDM patients had more severe muscle damage throughout the disease course compared with MDA5+ JDM patients and TIF1γ+ JDM patients. Furthermore, significant interaction effects of Group and Time on CK were observed in JDM patients. A three-year follow-up study revealed a higher relapse risk in NXP2+ JDM patients compared to MDA5+ JDM, TIF1γ+ JDM and NXP2+ adult DM patients. Conclusion The NXP2+ JDM patients experience more severe muscle damage, systemic complications, and higher relapse risks. Monitoring dynamic changes in CK and CMAS is essential for predicting disease progression and relapse risk.