Psoriatic arthritis

Genetic clue to link between psoriasis and PsA

An international study including Australian patients has identified a genetic variant that increases the risk of psoriatic arthritis in patients with cutaneous psoriasis.

The study of about 4,000 patients and almost 9,000 controls showed the risk of psoriatic arthritis increased in psoriasis patients with particular amino acids at one point in the HLA-B gene called position 97.

Position 97 on the gene has also previously been shown to be associated with ankylosing spondylitis, according to co-investigator Professor Matt Brown, a rheumatologist and immunogeneticist from QUT’s Institute of Health and Biomedical Innovation.

Professor Brown, told the limbic the findings did not have immediate clinical application.

“At this point there is not a specific treatment which targets these HLA groups but there may be in time when we can work out the actual antigens which are inducing the arthritis.”

He said predicting which group of patients with psoriasis will get psoriatic arthritis would be very useful.

“Both diseases are highly heritable and there is a strong overlap in the genes involved between the two. There has always been a lot interest in trying to distinguish what genes predispose more to psoriatic arthritis than to skin disease and vice versa.”

“Certainly in ankylosing spondylitis and in rheumatoid arthritis, the evidence suggests that if you treat people early, your treatment is more likely to be effective.

“So if we take patients with psoriasis, you are much more likely to treat the one at risk of getting psoriatic arthritis more aggressively in the hope you will actually prevent that occurrence.”

Professor Brown said the study did not distinguish between patients with predominately peripheral or axial disease – groups that would likely have a different pathogenesis.

Another future research step would be looking at non-HLA genes to see if they also distinguish between the different forms of psoriasis.

The study found that HLA-C*06:02 was associated with psoriasis but not psoriatic arthritis as previously thought. They said the age at onset of psoriasis had been a confounding factor in earlier studies.

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