Leptin has pro-inflammatory activity and may potentially influence the process of bone erosion in RA by favoring the release of pro-inflammatory mediators, which in turn may activate resident synovial cells to produce metalloproteinases (MPPs) and receptor antagonist of nuclear factor κB ligand (RANKL) for cartilage and bone degradation, respectively [13]. The gene discussed is LEP; the disease is rheumatoid arthritis.