Arthritis Arthritis Basics

Rheumatoid Arthritis: The Family Link

No one knows exactly what causes rheumatoid arthritis (RA), but researchers suspect that a combination of factors is involved. Hormones are thought to trigger the immune system to attack the joints and sometimes other organs. A virus or bacteria may also be at work. In recent years, genetics has proved to be a significant contributor to the disease.

Although scientists have yet to pin down exactly what role genetics plays, it has become increasingly clear that some people seem to have a genetic or inherited component that increases their chance of developing rheumatoid arthritis. What complicates the matter is that some people with rheumatoid arthritis do not have these particular genes. Others have these genes but never develop the disease. This somewhat contradictory data suggest that a person's genetic makeup can help doctors determine if a patient will develop rheumatoid arthritis, but they also prove that genetics is not the only factor. So far, researchers believe that many different genes appear to be involved, and each one, by itself, makes only a small contribution to one’s susceptibility to the disease. How these genes interact is believed to impact one’s individual disease risk.

Family Studies Support Genetic Link
Studies of families, as well as studies of identical and fraternal twins, further support the concept that inherited factors are important.

Investigators have already discovered that 2 to 3 percent of people who have a close relative with rheumatoid arthritis&mdashi.e. a parent, sibling or child&mdashwill eventually be diagnosed with the disease too.

Much of the research on families has been conducted by the North American Rheumatoid Arthritis Consortium. The consortium comprises researchers from 12 medical centers across the country. They have been carefully analyzing clinical findings and genetic material from 1,000 pairs of siblings who both have rheumatoid arthritis. By testing 400 different genetic regions, the researchers hope they can identify the specific genes associated with the disease. They also hope to pinpoint other genes involved in the spondyloarthropathies, an umbrella term for the class of arthritic conditions that affect the spine and other joints, as well as other rheumatic diseases.

So far, their research has confirmed an association between the development of rheumatoid arthritis and a cluster of genes involved in immune function called the human leukocyte antigen (HLA) complex.

HLAs refer to markers that influence the function of the body's immune system. The immune system uses the HLAs to differentiate self cells and non-self cells. A self cell is any cell that displays that person's HLA type and belongs to that person&mdashand therefore is not an invader. A cell that displays some other HLA type is non-self and is classified as an invader. HLA types are inherited. Some are thought to be connected to autoimmune disorders and other diseases.

Page 1 of 2 Next Page >>