This is the VOA Special English Health Report.

Rheumatoid arthritis is a painful disease that can destroy joints. Women are three times more likely to get it than men.

Rheumatoid arthritis is considered an autoimmune disease, a disease where the body attacks healthy cells. The exact cause is unknown. But in a recent study, an experimental drug showed signs of halting the disorder in laboratory mice.

Harris Perlman is a medical researcher at Northwestern University in Illinois. He says normally a protein in healthy immune cells causes the cells to die after they attack an invading virus or bacteria. But in rheumatoid arthritis, that protein is missing in some immune cells. Instead, the protein builds up in the joints and attacks cartilage and bone.

Professor Perlman developed what he calls a suicide molecule. It acts like the protein that directs cells to self-destruct. He says the suicide molecule halted and even reduced rheumatoid arthritis in 75 percent of the mice in the study. He believes the treatment could also work in people.

Current treatments for rheumatoid arthritis can reduce pain, but they do not work for everyone. They also have side effects such as an increased risk of infection. Harris Perlman says the new treatment produced no major side effects in the mice.

The study appeared earlier this year in the journal Arthritis and Rheumatism.

Arthritis is not a single disease. The MedlinePlus Medical Encyclopedia, a United States government website, says there are more than 100 different kinds.

Arthritis produces pain, swelling and limited movement in one or more joints. It involves the breakdown of cartilage. Joints need cartilage for smooth movement and to absorb shock when you put pressure on a joint.

Arthritis can be caused by injury, infection, an autoimmune disease or just long-term use. Some forms are curable, others are not. Some autoimmune forms of arthritis, if not treated, may cause joints to become deformed.

The most common form of arthritis, osteoarthritis, is more likely to affect older people. It most commonly affects the hips, knees or fingers. Overweight people have a higher risk of osteoarthritis. Other risk factors are repeatedly putting stress on a joint or having an earlier injury.

A physical therapist can design an individualized exercise program to reduce arthritis pain and support healthy joints. Getting plenty of sleep, reducing stress and eating a diet high in vitamins and minerals can also help.

And that's the VOA Special English Health Report. I'm Bob Doughty.

cartilage: the strong white flexible substance found between the joints in the body; a piece of this 软骨组织；（一块）软骨

osteoarthritis: a disease that causes painful swelling and permanent damage in the joints of the body, especially the hips, knees and thumbs 骨关节炎

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（来源：VOA 编辑：陈丹妮）