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Inherited Disorders and Birth Defects

Rheumatiod Arthritis

06/30/2006

Question:

I have RA for a little over 2 years now. My mother also has RA. I have a identical twin sister. What is the chances of my twin sister getting RA since I have it?

Answer:

Family studies and twin studies and have indicated that both genetic and environmental factors are involved in the development of rheumatoid arthritis (RA). Researchers know that RA can “run” in families and that there is a higher risk to develop RA if you have a first degree relative (a parent, a sibling or child) who has RA.

Studies have shown that 10 to 13% of people with RA have one or more first degree relatives who also with RA. This is about one and a half times higher than for people without a family history. A number of twin studies have been done and shown that there is a higher risk for an identical twin to develop RA if the other twin is affected than if the twins are fraternal. Studies have stated that the concordance (both being affected or both not affected) for identical twins was between 12 to 20% which is higher than what was seen for fraternal twins, which was about 3-4%.

The other major factor that has been found to increase the chance that both identical twins will develop RA is if they have the same HLA typing (genes that are involved in our immune system). There are some specific genes that have been found to be associated with RA.

The causes and genetic basis for RA continues to be researched. If you and your sister would like to discuss your specific risks about RA you may want to talk to a geneticist or genetic counselor for additional information. You can locate a genetics center near you at the National Society of Genetic Counselors Resource Center at the website listed below.

Related Resources:

National Society of Genetic Counselors Resource Center

For more information:

Go to the Inherited Disorders and Birth Defects health topic, where you can:

Response by:

Anne   Matthews, RN, PhD Anne Matthews, RN, PhD
Associate Professor of Genetics
School of Medicine
Case Western Reserve University