Cracking PsA’s genetic code

| Melissa Leavitt

Ever wish you had a crystal ball to tell you if your psoriasis is going to turn into psoriatic arthritis (PsA)?

Up to 30 percent of people with psoriasis go on to develop the swollen and achy joints known as psoriatic arthritis. Getting your psoriatic arthritis diagnosed and treated as early as possible could save you pain and disability down the road. But how can you predict whether your skin inflammation is going to spread to your joints?

The answer isn’t written in the stars. But it could be written in your DNA.

According to a recent study involving thousands of psoriatic disease patients, certain genetic factors may increase your chances of getting psoriatic arthritis. These particular genetic variants could be separate from genetic risk factors associated with skin psoriasis.

That tells scientists that psoriatic arthritis might have a different genetic basis than psoriasis  – and that a very specific part of your DNA may help determine whether or not you will develop psoriatic arthritis.

Separate risk factors for psoriasis and PsA

Psoriatic disease is caused by a combination of genetic risk factors and environmental triggers. So far, scientists have identified almost 70 genetic risk factors for psoriasis and 13 genetic risk factors for psoriatic arthritis, according to the study authors. These risk factors are found in genetic loci, which are specific places on a chromosome where genetic variants are located.

This study separated risk factors for skin psoriasis from risk factors for psoriatic arthritis. To do that, researchers first compared the genes of people with psoriatic arthritis to healthy controls. Next, they combined this data with previous genetic studies of psoriatic disease.

All in all, the analysis involved about 3,000 people with psoriatic arthritis and another 3,000 with skin psoriasis only. To be included in the skin psoriasis group, patients had to have psoriasis for at least 10 years with no signs of psoriatic arthritis.

Researchers identified several loci associated with psoriasis and psoriatic arthritis, according to the results. Among these, they found three that were more associated with skin psoriasis and two that were more associated with psoriatic arthritis.

Next step: Understanding how genetic changes affect our health

As scientists are able to pinpoint the specific genetic causes of psoriasis and psoriatic arthritis, they can study the effect these gene variants have on the way the body functions.

For example, according to the study one of the variants associated with psoriatic arthritis, known as IL23R, is located in a region affecting different immune cells and skin cells. The other variant associated with psoriatic arthritis, known as TNFAIP3, is in an area associated with different immune-mediated diseases.

Previous studies have also identified genetic risk factors specific to psoriatic arthritis and genes associated with particular psoriatic arthritis symptoms.

Ultimately, findings from these studies may be used to develop biomarkers, which are tests that can help doctors diagnose and treat psoriatic disease. For instance, biomarkers may one day predict which psoriasis patients will develop psoriatic arthritis or point the way toward new targets for treatment.

The international study, which was published in December in the American Journal of Human Genetics, involved genetic samples from Caucasian patients of European ancestry. Part of the samples came from the National Psoriasis Foundation’s National Psoriasis Victor Henschel Biobank, which is one of the largest collections of psoriasis DNA in the United States.

 

 

Popular Advance Online