Rheumatoid arthritis (RA) is the presence of chronic inflammation and symmetric erosive synovitis leading to joint deterioration and deformity. The onset is usually at a young age (15-45 years) and occurs more frequently in women than in men. RA is an autoimmune disease involving T-lymphocytes, B-lymphocytes, macrophages, and cytokines, but the exact etiology is unknown. T-lymphocytes produce proinflammatory cytokines and cytotoxic substances that lead to the erosion of bone and cartilage. Activated B-lymphocytes produce plasma cells which form antibodies that attack joint tissues. Macrophages release prostaglandins and cytotoxins to cause further injury and inflammation.
Early in the disease course, patients develop vague, generalized symptoms such as fatigue, malaise, diffuse musculoskeletal pain, and morning stiffness in joints that lasts for longer than 30 minutes. In the majority of cases, symptoms develop insidiously over weeks to months. The small joints of the hands, wrists, and feet are most likely to be involved and may appear swollen and feel warm to the touch. At later stages, joints of the fingers may become deformed because of the erosive effect of the disease on bones, tendons, and ligaments. RA patients occasionally have extra-articular involvement associated with their disease such as vasculitis, Sjögren’s syndrome, rheumatoid nodules, and pulmonary or cardiac complications.
There are no specific laboratory tests that establish a diagnosis of RA, but several tests suggest the diagnosis. About 60% to 70% of RA patients test positive for rheumatoid factor (RF), and 25% of patients test positive for antinuclear antibody (ANA). Erythrocyte sedimentation rates and C-reactive protein (CRP) levels may also be elevated, although these are nonspecific markers of inflammation. A complete blood count (CBC) may reveal anemia of chronic disease or thrombocytopenia.
According to the American College of Rheumatology, a diagnosis of RA is made when patients meet four of the following seven criteria for at least 6 weeks: morning stiffness (lasting >1 hour), swelling in three or more joint areas, swelling in the hand or wrist joints, symmetrical arthritis, rheumatoid nodules, positive RF, and radiological changes such as joint erosions or decalcifications.
RA varies in activity and severity among individuals and within the same patient. For this reason, it is important to assess disease duration, activity level, and prognostic factors for each patient. Disease duration is classified as early if less than 6 months, intermediate if 6 to 24 months, and long if for more than 24 months. Validated instruments (eg, RA Disease Activity Score, Simplified Disease Activity Index) are available to provide objective and consistent measures of disease activity. These instruments generate a disease activity score used to classify disease activity as low, moderate, or high, and this score is utilized for treatment decisions. Poor prognostic factors include active disease with high tender and swollen joint counts, increased RF level, extra-articular involvement, radiographic erosions, increased anti-cyclic citrullinated peptide antibodies, and functional limitation as assessed by the Health Assessment Questionnaire disability index.