Rheumatoid arthritis (RA) is a chronic inflammatory disease mediated by the production of several cytokines, which leads to the destruction of bone and cartilage tissue in multiple joints and to bone loss. Conventional radiographs (CR) are considered as the gold standard for diagnosis and follow up of joint changes in RA. But this method has low sensitivity to detect early erosive changes and is unable to evaluate periarticular bone loss.

High Resolution peripheral QCT (HRpQCT) enables the detection of erosions less than 0.5 mm in width or depth at metacarpo-phalangeal (MCP) joints. Using 3-D high resolution analysis of cortical bone erosions, this one is also able to evaluate the volumes of erosion and the evolution under treatments IL6 (6- interleukin) plays a major role in inflammatory process and bone damages related to RA. Tocilizumab (TCZ) is a humanized anti-IL-6R monoclonal antibody, developed and investigated in several clinical trials in RA. This biotherapy, in association with methotrexate (MTX) or given in monotherapy, is efficient in RA with inadequate response to MTX or anti-TNF b (tumor necrosis factor). TCZ reduces dramatically systemic inflammation, structural progression and improves clinical symptoms and quality of life.

Tocilizumab may help reducing bone erosions, periarticular osteopenia and systemic bone loss.

Inclusion Criteria:

• Active RA, < 10 years disease duration, diagnosed according to the ACR-EULAR 2010 classification criteria
• DAS 28 superior or equal to 3.2 despite DMARD or biological treatment (other than tocilizumab)
• Superior or equal to one joint erosion at the right or left MCP 2, 3 on X-rays
• Oral corticosteroid ≤ 10 mg/day prednisone or equivalent stable for at least one month
• RA patients eligible to subcutaneous Tocilizumab monotherapy

Exclusion Criteria:

• Treatment with zoledronic acid or denosumab (less than one year)

  • Intra-articular injection of corticosteroids at the MCP in the previous three months
  • Tocilizumab contra-indications in accordance with SPC (Summary of Product Characteristics) :Hypersensitivity to the active substance or to any of the excipients Active, severe infections including active tuberculosis Diverticulitis Active hepatic disease and hepatic Impairment including viral hepatitis Elevated Alanine Aminotransferase or Aspartate Aminotransferase >5×ULN Absolute neutrophil count < 0.5 × 10 exp 9 /L Platelet count < 50×10 exp 3 /μL,

General:

• Absence of informed consent
• Prior or planned joint surgery of the hands which might impact the interpretation of imaging assessments.