Aside from its role in the inflammatory process, there is much evidence that FOS has an important role in the regulation of osteoclastogenesis by RANK ligand signaling (25, 26), which in turn is demonstrated to have a crucial role in developing joint/bone destructive lesions in inflammatory arthropathies, such as rheumatoid arthritis and psoriatic arthritis (27). Here, FOS is linked to psoriatic arthritis.