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Rheumatoid arthritis (RA) is a chronic, inflammatory, multisystem autoimmune disease that targets the thin membrane (synovium) that lines the joints. Peripheral joints such as the wrists, knees, shoulders, hands and feet are most commonly affected. Although individuals of any age can present with RA, the usual age of onset is between 25 and 50 with a peak in the 40s and 50s.
RA develops when the immune system malfunctions, producing antibodies and immune complexes that attack healthy joint tissue. The result of this exaggerated immune response is thickening of synovial tissue and narrowing of the joint space. This leads to marked inflammation (synovitis) and tissue injury characterized by pain, stiffness, swelling, redness, and heat in and around affected joints. RA is usually symmetrical (i.e., affecting the same joints on both sides of the body simultaneously). Uncontrolled immune system inflammatory response can lead to total joint destruction and deformities. Unlike osteoarthritis (OA), systemic symptoms such as fever, weight loss, anemia, and malaise or weakness may be present, and joint destruction can become far more severe than in osteoarthritis. RA can also affect the major organ systems including the heart (pericarditis), lungs (interstitial lung disease, pleuritis), liver (hepatitis), eyes (dryness, inflammation of the sclera), blood vessels (vasculitis) and skin (nodules and ulcerations).
In 1987, the American College of Rheumatology established diagnostic criteria for the classification of rheumatoid arthritis. These include the presence of four of the following: (1) morning stiffness in and around joints that lasts for longer than one hour, (2) arthritis (pain and inflammation) with swelling of three or more joints simultaneously, (3) at least one of the joints referred to in (2) must be in the hand, (4) symmetric arthritis with simultaneous involvement of the same joint bilaterally, (5) rheumatoid nodules over bony prominences or near joints, (6) positive serum rheumatoid factor (RF), and (7) x-ray changes typical of RA. The first four criteria must have been present for a minimum of 6 weeks.
While the cause(s) of RA is remains unknown, several factors may play a role in disease development. These include a hyper-reactive immune system, association with specific inherited genes and acquired gene defects, hormonal factors, environmental exposures, and previous viral or bacterial infection.
Risk: Risk factors include female sex (the female to male ratio is 3:1) (King; Mercier), and genetic factors (the presence of specific tissue antigens such as class II MHC [major histocompatibility antigen], and human leukocyte antigens [HLA subgroups]). Incidence and Prevalence: Prevalence of RA in both the US and globally is approximately 1% (King; Firestein); at any given time approximately two million individuals in the US are affected by RA ("Comparative Effectiveness"). |