The macrophage migration inhibitory factor (MIF) is a key cytokine in the progression and pathogenesis of RA due to its ability to induce the expression of inflammatory cytokines and molecules that degrade tissue, as well as its capacity to promote proliferation and survival of fibroblast-like synoviocytes, stimulate neutrophil chemotaxis and regulate the process of angiogenesis and osteoclast differentiation [5,6]. This evidence concerns the gene MIF and rheumatoid arthritis.