We therefore confirm in this new set of patients the relationship between the anatomical observation of synovitis through US and the metabolic identification of these synovitis through 18F–FDG-PET/CT assessment, as shown earlier (Beckers et al., 2004; Beckers et al., 2006), as well as between the changes induced by rituximab, as already shown with anti-TNF-α treatments (Beckers et al., 2006). This evidence concerns the gene TNF and synovitis.