Rituximab in Systemic Sclerosis

Inclusion Criteria: * Systemic sclerosis fulfilling ACR or LeRoy's criteria * Active polyarthritis defined by \> 6/53 tender joints and \> 4/53 swollen joints * Ongoing first line therapy by prednisone (max 10 mg/d) and DMARDS (methotrexate, leflunomide, azathioprine or mycophenolate) * Birth control if applicable Exclusion Criteria: * Overlap syndrome defined by clinical symptoms and positive specific auto-antibodies (anti-CCP, anti-SSA, anti-DNA DNA anti-Sm) (Rheumatoid factors and anti-RNP are not exclusion criteria) * Past therapy with Rituximab. * Severe and uncontrolled disease with renal, liver or haematological (neutropenia \< 1500 / mm3) failures, pulmonary (FVC \< 50%) or cardiac insufficiencies (LVEF \< 50%) * Not stable corticosteroid therapy or cyclophosphamide use in the last 6 months * Infectious risk : viral infections by B or C hepatitis or HIV, hypogammaglobulinemia (\< 6 G/L), opportunistic infection or infection requiring IV antibiotics in the last 3 months. * Neoplastic solid tumor in the last 5 years * Drug or alcool abuses * Receiving patient or having received a biotherapy (anti-TNF, abatacept or tocilizumab) in the last 3 months (possible inclusion beyond 3 months)