The link between heredity and rheumatoid arthritis is unclear since there are different risk factors involved. It’s most definitely not a disease transmitted from one person to another, but studies have shown that the risk increases if a direct relative is diagnosed with RA.1
Your Genes May Affect Your Rheumatoid Arthritis Risk
A Swedish study, published in an article on the U.K. National Rheumatoid Arthritis Society (NRAS) website,2
revealed that the risk of being diagnosed with RA is three times more likely if you have a first degree relative with the disease, compared to first degree relatives of people from the general population.
This study, authored by Drs. Ian Scott and Sophia Steer, comes from a long line of research dedicated to finding out the connection between family genes and rheumatoid arthritis.
As early as the 20th century, there were already different studies with varying methods that analyzed generations of families diagnosed with RA during the ‘50s, ‘60s, and ‘70s.
The results did show different estimates due to the variety of methods used, but almost all of them found that a person’s risk for RA increases if he or she has relatives with the disease already.
Having a Twin With Rheumatoid Arthritis Is a Possible Link
Twin studies also provided evidence on the connection between RA and familial ties. Compared to non-identical twins, identical twins were more likely to both be diagnosed with RA, because they share 100 percent of their genes.
Researchers have also found a “heritability estimate” for rheumatoid arthritis based on studies conducted in Northern Europe, and the number falls between 53 and 68 percent. The heritability estimate is an “estimate of the extent to which genes explain the risk of disease in a population.”
Genes are a tricky subject to tackle, especially when they’re being analyzed to determine the cause of diseases like rheumatoid diseases. Even more so when it can be considered that there may be different genes that lead to this outcome, and not just a single one.
Recently, thanks to both technological advancements and the vast amount of patient and healthy control samples from around the world, it’s now possible to examine which of the various genes in the body are responsible for rheumatoid arthritis.
Scientists can do this by analyzing the differences in gene markers between people with or without RA.
Sadly, the main limitation in studying genes is that only the gene markers can be determined, but not the precise gene (or genes) that causes the disease.
What has been found out, however, is that there are two known genes that are linked to rheumatoid arthritis development: the HLA-DRB1 gene and the protein tyrosine phosphatase 22 (PTPN22) gene.
The HLA-DRB1 gene is “the strongest known genetic risk factor for RA development.” Several variants of this gene are linked with a higher risk of developing rheumatoid arthritis.
This is because the HLA genes produce proteins that assist the immune system in separating the body’s own proteins from foreign ones seeking to invade the human body.
Meanwhile, the PTPN22 gene also has a strong association with the development of rheumatoid arthritis, but it’s not fully determined how this gene influences the beginning of the autoimmune disease.