Recently, specific ligands targeting macrophage receptors such as CD20 receptor, interleukin-1 (IL-1) receptor, etc., have been investigated in the patients with RA using 99mTc-anti-CD20, 123I-IL-1ra and 124I-anti-CD20 illustrating the interest for molecular imaging in this type of pathology (Barrera et al., 2000; Tran et al., 2011; Malviya et al., 2012). This evidence concerns the gene MS4A1 and rheumatoid arthritis.