Does body composition matter in patients with systemic sclerosis?

Objectives: Body composition plays a significant role in various rheumatic and autoinflammatory diseases. The aim of our study was to assess the impact of muscle mass and subcutaneous adipose tissue quality and quantity in patients with systemic sclerosis (SSc). Methods: Adults with SSc referring to our tertiary center who underwent high-resolution chest computed tomography (HRCT) to assess pulmonary involvement were included. A semi-automatic segmentation of the subcutaneous fat and paravertebral muscle was performed at the level of the 12th dorsal vertebra, and body composition metrics were collected (subcutaneous fat and paravertebral muscle area and density). Stepwise linear regression analysis was applied to evaluate if body composition, demographics, and pulmonary function tests acted as predictors of mortality. Considering patients with muscle Hu values <30 as affected by myosteatosis, we used the odds-risk ratio to assess if it is associated with a higher risk of mortality. Results: Eighty-seven SSc patients (77 females, age 60±15 years, 61% affected by limited cutaneous SSc) were included. The linear model demonstrated that lower DLCO (p = 0.047), higher BMI (p = 0.013), higher density of the subcutaneous fat (p = 0.005), and lower skeletal-muscle index (p < 0.001) acted as predictors of mortality. Overall, 63 patients (72%) were affected by myosteatosis (ie, Hu < 30 Hu) and patients affected by muscle fat infiltration at CT showed a 3.345 times higher mortality risk (95% CI 0.396-28.295). Conclusion: Patients with systemic sclerosis are affected by myosteatosis and pre-sarcopenia and body composition seems to influence the overall outcome.