A paper published this week in the open access journal PLoS Medicine provides strong evidence that one specific part of the genome is associated with rheumatoid arthritis.
Rene Toes and colleagues from Leiden University Medical Center, the Karolinska Institute, and Celera studied four groups of patients and matched controls. They found a consistent association with one specific region of the genome -- a region on chromosome 9 that includes the two genes, complement component 5 (C5) of the complement system (a primitive system within the body that is involved in the defense against foreign molecules) and a gene involved in the inflammatory response, TNF receptor-associated factor 1(TRAF1) .
Rheumatoid arthritis is a very common chronic illness that affects around 1% of people in developed countries. It is caused by an abnormal immune reaction to various tissues within the body. As well as affecting joints and causing an inflammatory arthritis, it can also affect many other organs of the body. An association has been shown previously in humans with the part of the genome that contains the human leukocyte antigens (HLAs), which are involved in the immune response. In addition, previous work in mice that have a disease similar to human rheumatoid arthritis has identified a number of possible candidate genes including C5.