Your DNA
The genetics of rheumatoid arthritis
Rheumatoid arthritis is triggered by a combination of genetic and environmental factors. Slightly more than half of the risk of rheumatoid arthritis (53 percent) is inherited. This calculation is derived from studies of twins. Other studies demonstrate that inheriting certain genetic variants, or risk markers, can lead to an increased chance of developing rheumatoid arthritis over the general population.
We test for several common variants that have established associations with rheumatoid arthritis. One variant in particular in the region called the MHC (major histocompatibility complex), an area linked with auto-immunity, significantly raises the risk of developing rheumatoid arthritis if you have two copies. While this is an important component of genetic risk for rheumatoid arthritis, Navigenics does not currently include this region in its genetic analysis, as genetic results for this region are not currently reliable enough to meet our scientific standards.
Knowing if you have a hereditary predisposition to develop rheumatoid arthritis can enable you and your doctor to be alert for symptoms and work together to minimize the effects of this condition.
What we found for rheumatoid arthritis
We looked at five places on your genome where a one-letter difference in the genetic code affects your odds of rheumatoid arthritis. At each location, there are two markers, for a total of 10 possible risk markers. You have two of the 10 risk markers we looked for.
Rheumatoid arthritis
- You:
- 1.9%
- Avg:
- 3.3%
Your genetic markers
|
Gene or location 
|
Risk marker
|
Your markers
|
Odds ratio
|
Source
|
|---|---|---|---|---|
|
PTPN22
|
A | G G | 1.0 | American Journal of Human Genetics, 2004 |
|
chr6.138007111
|
C | C T | 1.33 | Nature Genetics, 2007 |
|
TRAF1
|
G | A G | 1.32 | New England Journal of Medicine, 2007 |
|
chr6.138048197
|
A | G G | 1.0 | Nature, 2007 |
|
STAT4
|
T | G G | 1.0 | New England Journal of Medicine, 2007 |
What it means
Everyone has some chance of developing rheumatoid arthritis. Each risk marker increases your odds by a different amount — some a little, some a lot. The "odds ratio" column in the chart above shows their relative impact.
About genetic markers
More than 99 percent of our genetic code is identical from person to person. The remainder is unique among individuals and gives rise to our diversity. DNA, the chemical instructions that determine our genetic code, is inherited from our parents and is composed of four biochemical bases that are represented by the DNA alphabet: A, T, G and C.
SNPs, or single nucleotide polymorphisms, are one-letter variations in our DNA. Each SNP (pronounced "snip") consists of two markers or variants, one inherited from each of our parents, and each marker has two possible versions, a risk version and a non-risk version. For example, at a given SNP, the base A may be the risk marker and the base G may be the non-risk marker. At another SNP, G may be the risk marker and T the non-risk marker.
The SNPs included in your Navigenics risk estimate have been reliably shown to be associated with diseases, although it is not known exactly how they contribute to the conditions. The degree of genetic risk you inherit is related, in part, to how many risk markers you have residing at each SNP — none, one (from one parent) or two (one from each parent). Just because you may have one or even two risk markers does not mean that you will definitely develop a given health condition, but it can raise your risk, especially if other lifestyle or environmental risk factors are present.