Psoriasis Psoriatic Arthritis

The Genetic Link to Psoriatic Arthritis

No one knows exactly why psoriatic arthritis (PsA) occurs, but doctors suspect that a combination of factors may lead to its development. One of the most intriguing factors is a person’s genetic makeup.

A little over a decade ago, a team of researchers linked the first genetic marker of psoriasis. Several other genes, which seem to be connected to both psoriasis and psoriatic arthritis, have been discovered since then. As researchers continue to investigate these links and study the genetic patterns involved in these diseases, they hope that eventually they will find specific treatments that will be able to disarm the role of genes in psoriasis and in the debilitating joint disease, psoriatic arthritis. Understanding the role of these genes may also prove useful in designing diagnostic methods to identify the diseases at the earliest possible stages.

In working toward that goal, it is important to know whether these diseases appear in a patient’s family history so that treatment may be started early and the progressive damage resulting from the disease may be halted. Even if the signs of psoriasis or psoriatic arthritis have not yet presented, their presence in a family member may signal a person’s predisposition toward developing the disease.

The Role of Family History
Several specific genes, which can be passed down from generation to generation, have been identified as playing a large role in the complicated process that leads to psoriasis and psoriatic arthritis. Scientists believe that at least 10 percent of the general population inherits one or more of these genes, however, only a small percentage of those people develop either disease. Only two percent to three percent of people encounter the "right" mix of genetics and environmental triggers that lead to the development of psoriasis and/or psoriatic arthritis. Those who have a genetic disease but do not have a family history of the disease may have inherited two genes from their father and two from their mother. However, if all four genes weren’t inherited, the disease may never develop in the patient.

Research suggests that as many as 40 percent of people with psoriatic arthritis have a history of psoriasis or psoriatic arthritis in their family and the closer the relative, the higher the risk of disease. For example, the closest relatives of patients with psoriasis or psoriatic arthritis have a 50-fold increased risk of developing the disease. In identical twins, there is a 75 percent chance that the other twin will have psoriatic arthritis. That risk drops to about one third for fraternal twins and even lower, to approximately 8 percent, for siblings.

As researchers delved further into the genetic patterns that develop among families with these diseases, they learned that patients whose fathers have psoriatic arthritis are twice as likely to get the condition as they would be if their mothers were affected.

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