When a virus or bacteria enters a healthy person, the immune system revs up to fight the invader. Once it’s gone, the body puts on the brakes to stop the immune response. In patients with lupus, it’s believed the immune system keeps going at full speed long after the threat is gone, causing damage to the body. Symptoms range from skin rashes and joint pain to strokes, seizures and organ failure.

This study reported in the August 1 online edition of Nature Genetics found that the genetic variation of a particular gene—known as TNFAIP3—leads to lupus and rheumatoid arthritis. This gene can be thought of as a critical brake mechanism for the immune system.  

The researchers examined the more than 20,000 genes in the human genome by performing over 300,000 genetic tests of DNA samples from 431 patients with lupus and compared the results to those of 2,155 healthy individuals. These results were then confirmed in a group of 740 lupus patients and their families. A North American consortium of clinical scientists and genomics experts did the study, including major contributions from researchers at the Montreal Heart Institute, the Université de Montréal and the University Health Network in Toronto.

The identification of TNFAIP3 and other genetic risk factors now indicate the specific biological pathways that need to be targeted in order to generate better diagnostic markers and effective therapies for both lupus and rheumatoid arthritis.