Rheumatoid arthritis (RA) is a chronic, inflammatory polyarthritis affecting peripheral synovial joints and extra-articular organs, including the heart, lung, kidney, eye, nervous system and blood vessels. There is destructive synovitis, effusions, cartilage damage, bone erosion and tenosynovitis. The onset is usually insidious. Morning stiffness is a prominent feature, along with fatigue and fever.
RA has a rising prevalence, affecting approximately 0.5% of the population with a higher prevalence in females. Other risk factors include genetic factors and exposure to cigarette smoke.
Many factors have been investigated as potentially exacerbating RA. These include air pollutants, silica exposure and dietary habits. The majority of women with RA experience a remission during pregnancy, suggesting hormonal immunological changes may be involved.
The 2010 American College of Rheumatology and European League Against Rheumatism criteria are used, with patients requiring a score of 6 or more to be classified as having RA. Points are scored for the number of large and small joints affected, positive rheumatoid factor (RF) and anti-citrullinated protein antibody (ACPA), abnormal CRP and ESR and duration of at least six weeks.
Approximately half of people with RA test positive for RF but it has a false positive rate of around 5%. ACPA has a lower false positive rate. Patients who test positive for both are more likely to have severe rheumatoid arthritis.
There are many pathologies presenting in a similar manner to RA. Palindromic rheumatism is an inflammatory arthritis causing attacks of joint pain and swelling similar to RA but between attacks joints return to normal. Lyme arthritis following a Lyme disease infection also has a similar presentation. Other inflammatory arthritides should also be considered.