Skeletal Muscle Involvement in Systemic Sclerosis

Abstract

Systemic sclerosis (SSc) is a systemic autoimmune connective tissue disease with great clinical and pathogenetic heterogeneity. Although skin is the most visible organ affected, skeletal muscles are affected in up to 96% of SSc patients and this is associated with a worse clinical outcome including increased mortality. Muscle involvement varies from patients experiencing myalgias, fibrosing myopathy to overlaps of SSc and myositis, a condition referred to as scleromyositis. In SSc muscle biopsies, muscular fibrosis, inflammation, microangiopathy and atrophy are observed, which is consistent with most prominent SSc pathophysiologic processes. The damage and fibrosis of the muscle tissue and the reduced ability of the body to build and repair muscle lead to a loss of muscle mass and strength. Studies show that patients with SSc have a higher prevalence of myopenia than the general population, but the exact cause is not yet fully understood. Partially, this phenomenon could be attributed to the disrupted activity of fibro-adipogenic progenitors, driven by alterations in the skeletal muscle microenvironment of SSc patients. These changes are also reflected in shifts in myokine secretion.