Rheumatoid Arthritis Hits the Joints and the Organs

When most of us think about arthritis, we're usually talking about osteoarthritis, the most common form of the disease, marked by the breakdown of the cartilage that cushions the joints. It affects an estimated 27 million Americans, the result of aging, obesity, stress or overuse. But there are actually about 100 different types of arthritis, including rheumatoid arthritis, or RA, which is one of 80 so-called autoimmune diseases.

Rheumatoid arthritis differs significantly from osteoarthritis. It occurs when the body's immune system begins attacking the lining of the joint capsule (called synovium), causing inflammation characterized by warmth, redness, swelling and pain. According to the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), the normally thin synovium becomes thick and makes the joint swollen and puffy to the touch.

"RA is not just limited to the joints," says Mary E. Cronin, MD, a rheumatologist and Associate Professor of Medicine at the Medical College of Wisconsin. "It can affect other organs: the skin, the lungs - both the lining of the lungs and the lung tissue itself - the liver, heart, eyes, nerves, muscles, blood vessels and, rarely, the kidneys." By contrast, patients with osteoarthritis do not experience inflammation of internal organs.

"RA patients with multiple organ systems affected tend to be those who have what's called rheumatoid factor in their blood, or those who form nodules on the skin or tendons, the cords or bands that connect muscles to joints. Blood tests show that about 75% of RA patients are positive for rheumatoid factor, and about 30% form nodules," Dr. Cronin says.

The number of Americans with RA is variously estimated at between 1.3 million and 2.1 million, about 1% or less of the population. Like many other autoimmune diseases, RA is more common among women, by a factor of 2 or 3 to 1 (the American Autoimmune Related Diseases Association puts it at 4 to 1).

Decline in New Cases?
NIAMS notes that some recent studies suggest that the overall number of new cases of rheumatoid arthritis actually might be decreasing, and scientists are investigating why. "It's intriguing," Dr. Cronin says. "If RA is declining, could it be linked to less smoking, or better control of infectious diseases, or some other event that might trigger RA? We just don't know."

Since higher clusters of RA have been found among some Native Americans, that points to the possibility that genetics could be involved in causing the body's immune system to turn against itself. Genetics are also an area of interest in exploring causes of other autoimmune disorders such as lupus and multiple sclerosis.

So far, however, no specific genes have been identified as causing RA to develop, Dr. Cronin notes. When an identical twin develops the condition, in 10% to 15% of cases, the other twin will also develop it. For fraternal twins and other siblings, the likelihood of more than one family member developing RA is about 3%. (With lupus, when an identical twin develops that disease, the chances the other twin will also develop it range from 25% to 50%.)

Rheumatoid arthritis affects people differently, according to NIAMS. "For some people, it lasts only a few months or a year or two and goes away without causing any noticeable damage. Other people have mild or moderate forms of the disease, with periods of worsening symptoms, called flares, and periods in which they feel better, called remissions. Still others have a severe form of the disease that is active most of the time, lasts for many years or a lifetime, and leads to serious joint damage, deformities and disability." Although RA can occur at any age, it most commonly develops in middle age.

"As with other autoimmune diseases, we don't know why the severity is so different among patients," Dr. Cronin says. She notes that, unlike lupus, RA patients who become pregnant often go into remission; with lupus, pregnancy can trigger flares. That raised the question of whether it might be beneficial to treat women with RA with estrogen, the female hormone. "It was tried in small clinical trials, but it made no difference," she says.

Causes and Triggers Under Study
Increasingly, research seems to indicate that vitamin D deficiency can play a role in setting off RA, but even more compelling, Dr. Cronin says, is evidence that the effects of smoking, which also is implicated in lupus, are even stronger in promoting RA.

New treatments for RA that have been developed in just the past decade show considerable promise, she adds. "Lots of new medications are in trials right now, and we're trying combinations of drugs with good results for preventing some deformities that can accompany RA. New medications have made a huge difference in patients. So we're hoping in the future to see fewer deformities."

"The treatments today are so much better than they used to be," she continues. "Those of us who've been in rheumatology for a while have seen how much the outcomes have improved. Our hope is that before long, severe deformities will only be those in textbooks, as pictures from the past. It's all making a big difference in our patients' lives."

Barbara Abel
HealthLink Contributing Writer

For more information on this topic, see the HealthLink article Autoimmune Disorders: When the Body Attacks.

Each year, Medical College of Wisconsin physicians care for more than 180,000 patients, representing nearly 500,000 patient visits. Medical College physicians practice at Children's Hospital of Wisconsin, Froedtert Memorial Lutheran Hospital, the Milwaukee VA Medical Center, and many other hospitals and clinics in Milwaukee and southeastern Wisconsin.