Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by inflammation in the lining of the joint capsule (synovium) and the lining of tendons. RA is a serious and often disabling condition that can cause chronic pain, permanent joint damage, and loss of joint function. Some research indicates that, instead of a single condition, rheumatoid arthritis may in fact be a group of different diseases that have several common features.
The immune system is a complex network of organs, cells (e.g., leukocytes, lymphocytes, phagocytes, B cells, CD8+ cells), and proteins that protects the body from disease and illness. It attacks foreign organisms (e.g., germs), identifies and destroys abnormal cells, and flushes dead and damaged cells out of the body. In autoimmune diseases such as rheumatoid arthritis, the immune system attacks normal cells in the body, causing damage and inflammation.
In rheumatoid arthritis, the immune system of the individual causes inflammation in the lining of the joint (synovium), which causes mild-to-severe pain, warmth, redness, and stiffness in and around the joint. Rapid cell division and growth occurs in the synovium (called pannus), causing thickening within the joint. Enzymes (proteins that affect chemical reactions) are released that digest cartilage and bone within the joint, causing the joint to become misshapen and misaligned.
Rheumatoid arthritis is a multisystemic disease, which means that in addition to the joints, it also can affect a number of organs in the body (e.g., skin, eyes, heart, lungs).
Incidence and Prevalence of Rheumatoid Arthritis
According to the Arthritis Foundation, RA is the second most common type of arthritis. It affects approximately 1.3 million people in the United States, and about 70% of patients who have the disease are women. Rheumatoid arthritis usually develops between the ages of 30 and 50, but it can occur at any age.
Rheumatoid arthritis also affects men and children (called juvenile rheumatoid arthritis and also juvenile idiopathic arthritis). In women who are of childbearing age, RA often improves during pregnancy, but symptoms may increase in severity after the patient gives birth.