Rheumatoid arthritis.

Rheumatoid arthritis (RA) is a chronic inflammatory multisystemic disease of unknown etiology and autoimmune nature that predominantly affects peripheral joints in a symmetrical fashion. Although much progress has been made in understanding the pathophysiology of RA, its etiology remains unknown. Tumor necrosis factor (TNF)-α and interleukin (IL)-6 play the important roles in the pathogenesis and maintenance of inflammation in RA. The presence of anti-citrullinated peptide antibodies aids in the diagnosis in patients with undifferentiated polyarthritis and is associated with a more aggressive RA. The natural history of RA causes joint deformity and disability, as well as reduced life expectancy, both due to increased cardiovascular risk, pulmonary involvement, infections, iatrogenesis or tumors. Early diagnosis and the use of targeted drugs to induce early remission have improved the RA prognosis.