Overview of epidemiology, pathophysiology, and diagnosis of rheumatoid arthritis.

Rheumatoid arthritis (RA) is a common autoimmune systemic inflammatory disease affecting approximately 1% of the worldwide population. The interaction of genetic and environmental factors results in a cascade of immune reactions, which ultimately lead to the development of synovitis, joint damage, and structural bone damage. These, in turn, lead to pain, disability, and emotional, social, and economic challenges. A number of extraarticular manifestations and comorbidities are present in patients with RA, which result in increased mortality. The American College of Rheumatology and European League Against Rheumatism recently published updated disease classification criteria in an effort to identify RA earlier so that effective treatment can be employed to prevent irreversible changes.