Cachexia

A condition characterized by muscle wasting, fatigue, weakness, and sometimes weight loss that is associated with certain serious inflammatory conditions, including cancer, AIDS, and rheumatoid arthritis (RA). Cachexia is thought to affect more than 5 million people in the United States. When it accompanies RA, the condition is sometimes called “rheumatoid cachexia.” By some estimates, two-thirds of people with RA in the United States are affected by cachexia.

People with rheumatoid cachexia lose some of their skeletal muscle, causing muscle weakness and making it more difficult to carry out day-to-day functions. Some people with rheumatoid cachexia also gain fat, negating any weight lost through muscle wasting and increasing the risk of disability. There are many possible causes of rheumatoid cachexia. Reduced physical activity, whether caused by joint pain, fatigue, or fear of further injuring the joints, may be one. Several other factors may also be involved.

For example, cytokines, the body’s chemical messengers, may play a role in the development of cachexia. Specifically, elevated levels of proinflammatory cytokines such as tumor necrosis factor–alpha and interleukin-1 are common in people with RA and are believed to be an important cause of cachexia because they change the way the body breaks down proteins. (Proteins make up a large part of human body cells and are also part of compounds, such as hormones and antibodies, that play active roles in the body. Breaking down and replacing proteins is part of the body’s normal repair and maintenance cycle.)

There is no known cure for rheumatoid cachexia, but research suggests that some interventions might help to relieve it. One is exercise, including high-intensity strength training. Studies suggest that strength training is a safe and effective way to increase strength and reduce fatigue and joint pain in people with RA. Also, a special diet or dietary supplements might help counteract the loss of muscle in people with rheumatoid cachexia. For example, a small study done in 2005 found that supplements with certain amino acids increased muscle mass in people with RA. Because proinflammatory cytokines seem to play such an important role in cachexia, medicines that target cytokines — examples are etanercept (Enbrel) and infliximab (Remicade) — would seem to be useful drugs for treating it. Yet to date, studies have not shown that these drugs can reverse cachexia.

Robert S. Dinsmoor is a medical editor and writer based in Massachusetts.

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