The direct link between heredity and rheumatoid arthritis remains unclear. While RA isn’t contagious, initial evidence shows that the risk for this debilitating disease increases by three times if a direct relative has already been diagnosed. These results came from a study spearheaded by Drs. Ian Scott and Sophia Steer, which involved Swedish subjects, and was published in the U.K. National Rheumatoid Arthritis Society’s (NRAS) website.
Scott and Steer’s study is another addition to a long line of research dedicated to discovering the role genetics play in RA development. As early as the 20th century, there were studies analyzing members of families diagnosed with RA, paving the way for more research during the ‘50s, ‘60s and ‘70s.
Since most of the studies utilized different methods, results showed various estimates. However, there was a common factor between the results, and it was determined that your risk for RA increases if you have relatives who were diagnosed with the disease.1
What Is a Heritability Estimate?
Researchers have also found a “heritability estimate” for rheumatoid arthritis based on studies conducted in Northern Europe, with the number falling between 53 and 68 percent. The heritability estimate may explain the probability that genes may cause a certain disease to occur in a population. This concept is considered an estimate because in some cases, genes aren’t the sole factor for triggering the disease. Some genes may also interact with the environment and ultimately lead to the onset of a particular disease.
Aside from examining RA risks between family members, some researchers have studied the potential link between RA and genetics among twins. It was revealed that identical twins, because they share 100 percent of their genes, are more likely to be bothdiagnosed with RA.2
Which Genes Are Linked to RA?
According to a 2015 article from the Japan Academy, these are the five genes that have been linked to rheumatoid arthritis:3
- PADI4 (peptidylariginine deiminase type 4)
- PTPN22 (protein tyrosine phosphatase 22)
- CCR6 (chemokine [C–C motif] receptor 6)
- FCRL3 (Fc receptor-like 3)
The Challenge in Studying Genes Linked to RA
The NRAS emphasizes that genes are a tricky subject to tackle, especially when they’re being analyzed to determine the cause of rheumatoid diseases. The good news is that factors such as technological advancements and healthy patient control samples sourced from around the world have made it possible for researchers to determine genes responsible for RA.
The main method in checking these possible genes involves inspecting gene markers among people with and without the disease. However, a major limitation in this goal is the tendency for only the gene markers to be determined, and not the precise gene (or genes) that causes the disease.4