Genetic Roots of Psoriatic Arthritis

Much of the study of psoriatic arthritis has focused on its links to psoriasis, a disease affecting the skin. According to the Annals of Rheumatic Disease, anywhere from 6 to 40 percent of people with psoriasis also develop psoriatic arthritis. In addition, there’s a strong genetic component to psoriatic arthritis: People with a family history of the disease were around 27 to 48 times more likely to develop it themselves. This strong tendency for people to inherit the genes that cause the disease or make it more likely to develop – higher than most autoimmune diseases – suggests that genetic testing is key.

No one gene has been identified as causing psoriatic arthritis. However, one possible gene variant that may be connected to the disease is MICA-A9, located on chromosome 6. In July 2010, the PsoriasisDX Genetic Test was approved in Europe to test for psoriatic arthritis; the test is also currently performed by some U.S. doctors. In addition, a recent study in Iceland showed a possible link to a variant on chromosome 16q and psoriatic arthritis, and other recent studies show a higher percentage of people with psoriatic arthritis affecting the spine also have the gene variant HLA-B27.

Recent studies focusing on possible genes only reveal that a person with the gene is more likely to develop psoriatic arthritis. That doesn’t mean that the person will develop the disease. Often, the disease must be triggered by some other environmental factor, which could include high levels of stress, an infection or use of oral steroid drugs for some other purpose.

Research is currently being conducted to explore the possibilities of gene therapy – the alteration, removal or insertion of genes into a person’s body to treat diseases or problems – for treating various forms of arthritis. Gene therapy is one of the most exciting areas of medicine, as it holds the possibility of addressing genetic causes of devastating diseases without the dangerous side effects of current drugs.

The research isn’t without controversy. A patient’s death in one study was later revealed not to be a result of gene therapy, but the death caused increased scrutiny of the cutting-edge field. Relatively few clinical trials are being conducted at this time, mainly because people are satisfied with their current biologic drugs, and because of the expense of studies.

However, the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) recently gave a $1.6 million grant to a Harvard researcher for studying gene therapy in osteoarthritis, and a small study on gene therapy in rheumatoid arthritis patients showed promising results in 2009.