Rheumatoid Arthritis (RA) and Lupus have long been suspected to have a common genetic component. Narrowing the field of possibilities to just one likely candidate has taken researchers years to accomplish. The suspected gene is STAT4, but it is too early to tell what impact it will have in therapy for both diseases. This is the first time a gene has linked RA and Lupus.

The STAT4 gene encodes a protein that plays an important role in the regulation and activation of certain cells of the immune system. According to researchers, patients who carry 2 copies of the disease-risk variant form of the STAT4 gene have a 60% increased risk for RA. Lupus patients were twice as likely to have the risk variant form of STAT4 than those in the control group who had neither RA nor lupus.

Both diseases are considered autoimmune diseases in which the body’s immune system attacks healthy tissue. In RA, the immune system attacks the linings of the joints and sometimes other organs. In lupus, it attacks the internal organs, joints and skin. If not well managed both diseases can lead to significant disability.

It is not known what role STAT4 has in the development of either disease, but it appears to play a fundamental role and is an excellent springboard for scientist to launch into further studies.