Is Myopenia or Myosteatosis Clinically Relevant in Systemic Sclerosis? Skeletal Muscle Assessment Using Computed Tomography.

Objectives: Systemic sclerosis (SSc) is a chronic autoimmune disease characterized by fibrosis, vascular damage, and immune dysregulation, often leading to muscle abnormalities. This study aimed to evaluate the prevalence of myopenia and myosteatosis in SSc patients using computed tomography (CT) and their associations with clinical features, including lung disease and esophageal dilatation.

Materials And Methods: SSc patients followed at Gazi University Rheumatology Clinic (2000-2024) who had thoracic CT imaging were included. Muscle mass and density were assessed at the L1 vertebral level. Skeletal muscle area (SMA) and skeletal muscle radiation attenuation (SMRA) were measured to identify myopenia and myosteatosis. Lung disease involvement and widest esophageal diameter (WED) were assessed via CT. Statistical analyses explored correlations between muscle metrics and clinical variables, with multiple linear regression identifying predictors.

Results: Among 95 patients (54.7% diffuse SSc, 45.3% limited SSc; mean age 57.04 ± 13.65 years; female-to-male ratio 8.5:1), myopenia and myosteatosis prevalence were 27.3% and 41.1%, respectively. Myosteatosis was associated with female sex (p = 0.001), older age (p = 0.001), higher BMI (p = 0.043), and inflammation markers (CRP, ESR). Myopenia correlated with BMI (p = 0.001) but not clinical outcomes. Higher WED correlated with lower SMRA (p = 0.001). BMI predicted muscle mass (R² = 0.42), while age, gender, and BMI determined SMRA (R² = 0.67, p < 0.001).

Conclusions: Myosteatosis was more prevalent and strongly associated with clinical features, including lung disease and esophageal dilatation, than myopenia, underscoring the importance of muscle quality.