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By Root 9619 0

from these invaders by detecting and killing them. But if your immune system is not working properly, it can mistake your body’s own cells for foreign invaders and attack them. This process—the immune system attacking itself—is called autoimmunity. Doctors have not yet discovered exactly why the immune system treats some parts of the body as harmful invaders, but they think that certain people have a genetic predisposition to autoimmunity. Such susceptible people develop an autoimmune disorder when they are exposed to an environmental trigger such as an infection, certain drugs, or, in some women, pregnancy.

An autoimmune disorder can affect almost any part of the body, and the specific symptoms depend on which organs are targeted. But when the immune system attacks, it almost always produces inflammation, and this inflammation can damage the body. Autoimmune disorders are unpredictable. In some people they last for a few months or years and then go away on their own. Other people experience periodic flare-ups—times when symptoms get worse—followed by intervals during which they feel better. Still others have a disorder that is active most of the time, lasts for years, and causes severe damage.

Autoimmune disorders affect many parts of the body

Autoimmune disorders cause the immune system to mistakenly attack cells and organs in the body as if they were invading microorganisms. Many different parts of the body can be affected. Some autoimmune disorders, such as rheumatoid arthritis, affect only specific parts of the body, such as the joints, while others are systemic, affecting the entire body. For example, some forms of lupus can cause serious damage to the lungs, heart, kidneys, and brain.

Rheumatoid Arthritis

Rheumatoid arthritis is a chronic autoimmune disorder that causes inflammation, pain, swelling, stiffness, and loss of function in the joints. In rheumatoid arthritis, the immune system attacks the membrane called the synovium, which lines joints. The synovium becomes inflamed, causing joint pain, warmth, redness, and swelling. The cells of the synovium begin to grow and divide abnormally, and start to invade and destroy the cartilage and bone inside the joint. The surrounding muscles, ligaments, and tendons become weak and unable to support the joint. Over time, untreated deterioration of joint and bone tissue produces deformities in the joint, making it difficult for a person to lead an active, independent life.

The joints that are most frequently affected are the small ones in the hands and feet, mainly the knuckles and toe joints, but rheumatoid arthritis can affect any joint, including the wrists, knees, ankles, or neck. It occurs less often in the spine or hips, which are much more susceptible to osteoarthritis (see page 996). Osteoarthritis results from stress on the joints over time and is not an autoimmune disorder. Certain characteristics distinguish rheumatoid arthritis from other types of arthritis. For example, rheumatoid arthritis always occurs in a symmetrical pattern—if one knee or wrist is affected, the knee or wrist on the other side of the body is also affected. Joint inflammation usually affects the wrist and finger joints closest to the hand. Unlike osteoarthritis, rheumatoid arthritis can affect parts of the body other than the joints, causing inflammation in the eyes, heart, lungs, and blood vessels, and changes in the tissues that lie just beneath the skin.

Rheumatoid arthritis in the hands

Rheumatoid arthritis can severely deform the joints of the hands, making routine daily activities difficult. The finger bones typically curve away from the thumb side of the hand.

Rheumatoid arthritis affects more than 2 million people in the United States, two thirds of whom are women. The disorder occurs in all racial and ethnic groups and most often first appears in middle age, although it can develop in a person’s 20s or 30s. Juvenile rheumatoid arthritis (see page 434) can affect children between the ages of 6 months and 16 years.

Symptoms

The symptoms of rheumatoid arthritis