Muscle involvement is poorly described in patients with systemic sclerosis (SSc) . The prevalence of muscle damage is evaluated at 5-95 % of SSc patients, particularly due to variable definitions depending on the series in the scientific litterature. Muscle clinicobiological and histological presentation an response to immunosuppressive treatments are highly variable. Muscle involvement defined by creatinine kinase (CK) elevation, the presence of electromyography (EMG) abnormalities and/or muscle magnetic resonance imaging (MRI) hyperintensities and/or muscle biopsy inflammation appears to be associated with diffuse SSc, the presence of cardiac damage, and anti-PM-Scl antibodies. The main objective is to describe muscular manifestations associated with SSc. Secondary objectives are: * to compare characteristics between SSc patients with and without muscle involvement * to determine homogeneous groups of SSc patients with muscle involvement