This study found a block of genes that increases risk for both rheumatoid arthritis and systemic lupus erythematosus, suggesting a shared pathway for these illnesses.

Rheumatoid arthritis (RA) is the most common cause of inflammatory arthritis in adults. Studies of twins indicate that about half of RA risk is genetic and half is environmental. The HLA region, located on chromosome 6, is involved in immune function and is a known contributor to the risk of rheumatoid arthritis. Researchers suspected that the STAT1-STAT4 region on chromosome 2 was likely to contain susceptibility variants as well.

Researchers tested 13 genes in chromosome 2 for their association with rheumatoid arthritis. In particular, they focused on the STAT1-STAT4 region in chromosome 2 in a group of 1,620 North American patients with rheumatoid arthritis and 2,635 healthy controls. They then statistically reproduced the most promising variants in 1,529 Swedish rheumatoid arthritis patients and 881 healthy controls, as well as 1,039 patients and 1,248 healthy controls from three groups of lupus patients.

The researchers found that a specific variant located within a block of variants in STAT4 raised the risk for developing both lupus and rheumatoid arthritis, supporting the idea that common risk genes and pathways can underlie multiple autoimmune disorders. Possessing two copies of the risk variant, compared to having none, more than doubled risk for lupus and raised the risk for rheumatoid arthritis by 60 percent.

More: To read an abstract of this paper on the medical database PubMed, click here.