In autoimmune diseases, the immune system attacks the body.Rheumatoid arthritis and lupus can affect many parts of the body, including the joints.
Researchers now report that some rheumatoid arthritis patients and lupus patients share a variation in the STAT4 gene, which is part of the immune system.
The researchers included Peter Gregersen, MD, who directs the Robert S. Boas Center for Genomics and Human Genetics at the Feinstein Institute for Medical Research in Manhasset, N.Y.
Gregersen tells WebMD that he suspects that STAT4 and other genes "are common susceptibility variants for groups of diseases."
But he cautions that the immune system is so complex that scientists haven't yet found all the gene variations that affect rheumatoid arthritis, lupus, and other autoimmune diseases.
"You can get to the same clinical appearance by multiple genetic mechanisms. Does that translate into similar mechanisms at the functional level that become targets for new therapies? That is the big question," says Gregersen.
Rheumatoid Arthritis, Lupus Gene Study
Gregersen and other scientists in the U.S., Sweden, and South Korea compared DNA in and around 13 genes that had previously been linked to rheumatoid arthritis.
The scientists found that variations in the STAT4 gene were more common in more than 3,100 rheumatoid arthritis patients than in some 3,500 people who don't have rheumatoid arthritis.
Those same variations in the STAT4 gene were also more common among 1,039 lupus patients than among more than 1,200 people without lupus.
The findings appear in tomorrow's edition of The New England Journal of Medicine.
With additional reporting by WebMD Senior Medical Writer Daniel J. Denoon.