What is Rheumatoid Arthritis?

Medically Reviewed

Rheumatoid arthritis affects approximately 1.5 million Americans, and it affects 2.5 times as many women as men. The condition often begins between ages 30 and 60 in women and later in life in men, but it can develop at any age.

The major distinguishing characteristics of rheumatoid arthritis are that it is autoimmune, inflammatory, chronic and systemic (affecting the entire body).

Autoimmune. An immune-system attack that the body launches upon itself is termed autoimmune. For some unknown reason, the immune system becomes “confused” and begins to interpret molecular signals from normal body tissues as if they were coming from harmful infectious bacteria or viruses. In rheumatoid arthritis, the chief target of this immune system attack is the synovial membrane, the lining of the joints that connect parts of the skeleton.

Inflammatory. When the white blood cells of the immune system attack the synovial membrane, they begin to release the same poisonous substances that kill bacteria and viruses during an infection. The result is a series of chemical changes that produce the same local symptoms that occur with an infection—the combination of heat, swelling, pain and redness known as inflammation.

Chronic. Like osteoarthritis, rheumatoid arthritis is a chronic disease; the autoimmune attacks can continue indefinitely. However, rheumatoid arthritis is more crippling than osteoarthritis. As the disease progresses, continued inflammation causes the synovial membrane to thicken. An area of inflammatory cells (a pannus) often starts to form at the point where the synovial membrane joins the cartilage.

Continued release of enzymes and growth factors by white blood cells, along with growth of the pannus, can erode cartilage, tendons, ligaments and even bones within the joint capsule. As rheumatoid arthritis progresses, the ever-growing pannus can further limit joint motion. Inflammation of tissues surrounding the joint may eventually cause permanent joint damage and deformities.

Systemic. The effects of rheumatoid arthritis are not limited to the joints; they can have consequences throughout the body. As a result, people who have the disease often lose their appetite, tend to run a low fever and feel generally unwell, as if they have the flu, and are frequently fatigued. Rheumatoid arthritis is a serious systemic illness, and without proper treatment, it can lead to significant disability and premature death.