Longitudinal ultrasound assesment of skeletal muscle ın systemic sclerosis: association with disease activity and severity

OBJECTIVES: Systemic sclerosis (SSc) is an autoimmune fibroinflammatory disease that may predispose to the development of muscle loss through chronic inflammation and functional limitation. Longitudinal assessment using ultrasound provides insights into muscle loss and its association with disease activity and severity. This study sought to evaluate early muscle loss using ultrasound in SSc patients and investigate their relationship with disease activity and severity. METHODS: A longitudinal study was conducted in 52 SSc patients, with muscle thickness at various sites, including biceps brachii, triceps brachii, medial gastrocnemius, and the rectus femoris measured at 0, 6, and 12. months using ultrasound. Associations with disease activity, Medsger's Severity Score and modified Rodnan skin score (mRSS) were analyzed. The diagnostic value of changes in muscle thickness for determining disease activity was assessed using ROC curve analysis. RESULTS: A significant inverse correlation was identified between the change in gastrocnemius muscle thickness and disease activity over the initial 6-month period (r=-0.36, p = 0.026). A significant relationship was found between the difference in mRSS and the difference in biceps brachii muscle thickness between baseline and 6 months (r=-0.33, p < 0.05). Decreasing muscle thickness paralleled increasing severity scores. ROC analysis for gastrocnemius muscle indicated moderate discriminative performance for detecting clinically relevant muscle changes. CONCLUSION: Longitudinal ultrasound assessment effectively reflects progressive reduction in muscle thickness in SSc, correlating with disease activity and severity. These findings highlight ultrasound as a practical, non-invasive tool for early detection and monitoring, potentially capturing subclinical changes, specifically a decrease in muscle thickness, in SSc.