Rheumatoid Arthritis

Background
Rheumatoid arthritis (RA) is a systemic autoimmune inflammatory disease characterized by synovitis and serositis (inflammation of the lining surfaces of the joints, pericardium, and pleura), rheumatoid nodules, and vasculitis. The hallmark feature of the disease is persistent symmetric polyarthritis (synovitis) that affects the hands and feet, although any joint lined by a synovial membrane may be involved. In addition to articular deterioration, systemic involvement may lead to weight loss, low-grade fever, and malaise. The severity of RA may fluctuate over time, but chronic RA most commonly results in the progressive development of various degrees of joint destruction, deformity, and a significant decline in functional status.
Juvenile rheumatoid arthritis (JRA) is the most common form of childhood arthritis. The cause remains unknown. For most patients, the immunogenic associations, clinical pattern, and functional outcome are different from adult onset RA.
The diagnostic criteria for JRA are onset occurring when younger than 16 years, persistent arthritis in one or more joints for at least 6 weeks, and exclusion of other types of childhood arthritis. The key points that characterize the diagnosis of JRA are as follows:
Arthritis must be present. Arthritis is defined as the presence of swelling, the presence of effusion, or the presence of 2 or more of the following signs: limited range of motion (ROM), tenderness, pain on motion, or joint warmth.
Arthritis must persist for at least 6 weeks.
Other causes of chronic arthritis in children must be ruled out.
No specific laboratory or other test can establish the diagnosis of JRA.

Pathophysiology
The diagnosis of RA must be considered in any patient with polyarticular inflammatory arthritis, especially if both the hands and feet are involved. The early phase of the disease is characterized by the following features:
Joint swelling that may affect joint margins
Joint tenderness upon palpation
Systemic malaise
Loss of energy
Severe morning stiffness that limits function and generally lasts more than an hour
A classic feature of the illness is the symmetry of involvement. If synovial-based inflammation persists over time, permanent damage to tendons, ligaments, and cartilage and subchondral bone destruction occur with resultant joint deformity and limited motion. Inflammation and deformity also are nearly always seen in the hands and feet. However, involvement of the knees, hips, and shoulders accounts for significant morbidity that leads to work disability in a large percentage of patients.
A major difference in the pathophysiology of RA versus osteoarthritis or mechanical joint problems is the presence of extensive synovial inflammation. The characteristic signs of inflammation were stated by Celsus as "rubor et tumor cum calore et dolore," meaning redness and swelling with heat and pain. Galen later added "et functio laesa" (disturbed function) to the characteristic signs of inflammation. Joint tenderness, swelling, stiffness, and pain on motion are the features of inflammation experienced by patients with RA.

Frequency
United States
The prevalence rate of RA is approximately 1% of the population (range 0.3-2.1%).
Race
RA is observed throughout the world and affects persons of all races.
Sex
Women are affected approximately 3 times more often than men. Sex differences diminish in older age groups.
Age
Although RA can occur at any age, the incidence increases with advancing age. The peak incidence of RA occurs in individuals aged 40-60 years.

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