Understanding the links between psoriasis and psoriatic arthritis

Irish patients sought for international study aiming to better understand the connections between the two conditions

Most people are familiar with the common skin condition, psoriasis, which causes a scaly, lumpy rash on the backs of elbows, front of knees, the scalp and other parts of the body. But, the autoimmune disease, psoriatic arthritis, which about a third of people with psoriasis also suffer from, is much less well known.

There is currently no diagnostic blood test for psoriatic arthritis.

A group undertaking an international study is seeking to better understand the links between the two conditions, with the aim to find out why some people with psoriasis go on to develop psoriatic arthritis and what treatment would work best to halt its development.

Prof Oliver Fitzgerald, research professor in rheumatology at the Conway Institute at University College Dublin and Prof Steve Pennington, professor of proteomics at UCD, are leading the Irish arm of the Hippocrates consortium study. “We have about 350 patients so far, but we are keen to have 2,000, so we are interested in anyone aged 18 or over diagnosed with psoriasis to join the study,” says Prof Fitzgerald.


Those who choose to partake in the study will be required to fill out a questionnaire every six months over three years. Details required are the extent of their psoriasis, current treatments and if they have noted any emerging symptoms of arthritis.

Prof Fitzgerald says that, ultimately, the identification of distinct biomarkers for psoriatic arthritis could lead to earlier treatment and possibly even prevention of the condition. The researchers also hope to identify a potential blood test which would diagnose psoriatic arthritis. “It shares some symptoms of joint pain, swelling and loss of function with rheumatoid arthritis but it has some features which are different,” says Prof Fitzgerald.

These distinguishing features include how the toes and fingers swell to look like little sausages, pain and stiffness in the spine that gets worse with rest yet improves with exercise. And pain and inflammation in the tendon and ligaments attached to the bone, for example, in the Achilles’ tendon attached to the heel.

“I always tell my students that you have to be hunting for psoriatic arthritis to find it and the psoriasis doesn’t always have to be very severe to have it. It could be between the buttocks, under the arm pits or under the breasts in women,” he explains.

Some studies have found that scalp psoriasis may be a risk factor for psoriatic arthritis. And both conditions also have a genetic component as they tend to run in families. A delayed diagnosis can result in treatments starting later, allowing the joints to deteriorate further in the intervening time.

Some of the newer biologic treatments – seen as a game changer in the treatment of rheumatoid arthritis – work very well in clearing the psoriasis but don’t improve the condition of the joints. “The problem is that we don’t know which patients suit which treatment. We also want to find this out in the study,” says Prof Fitzgerald.

The information submitted by those who join the study will be reviewed every six months and individuals will be given feedback on their submissions.

“We will advise those who we identify with symptoms of psoriatic arthritis to seek medical assessment, but we also advise people with psoriatic to remain as active as they can to prevent further loss of function of their joints,” he adds.

  • See our new project Common Ground, Evolving Islands: Ireland & Britain
  • Sign up for push alerts and have the best news, analysis and comment delivered directly to your phone
  • Find The Irish Times on WhatsApp and stay up to date
  • Our In The News podcast is now published daily – Find the latest episode here
Sylvia Thompson

Sylvia Thompson

Sylvia Thompson, a contributor to The Irish Times, writes about health, heritage and the environment