Researchers studied more than 2,500 people with lupus and found that people with the disease were more than two to three times as likely to have a particular variant of a gene called PDCD1.
The study appears in the December issue of Nature Genetics.
Estimates vary, but lupus is thought to affect about one in every 2,000 people in Western countries and most commonly strikes young women between the ages of 15 and 40.
Previous studies have shown that mice that lacked PDCD1 developed a lupus-like disease, but researchers say this is the first study to identify the genetic difference in people with lupus. The mutation was particularly common in European and Mexican people.
However, the abnormal gene is associated with only some people with lupus -- 12% of European and 7% of Mexican lupus patients have this lupus gene. Researchers found this gene in only 2% to 5% of people without the disease.
Study researcher Marta Alaracón-Riquelme of the University of Uppsala in Sweden says this gene is already known to affect the ability of the immune system to recognize its own cells from others, and any alteration of the gene might contribute to the exaggerated immune response that is found in lupus. -->