Researchers identify important genetic markers which differentiate psoriasis and psoriatic arthritis

Psoriatic arthritis is a chronic inflammatory arthritis, with figures suggesting it affects around 14% of those in the UK with psoriasis. It typically causes affected joints to become inflamed, stiff and painful.

The risk of a person developing psoriasis and psoriatic arthritis are heavily influenced by a person’s genetics. To date researchers have identified 49 genetic markers for psoriasis; however research into identifying the markers associated with the development of psoriatic arthritis has been more challenging.

The research, a collaboration between researchers from the BRC’s Musculoskeletal and Dermatology Theme, was led by Research Fellow, Dr John Bowes from The University of Manchester. Working with colleagues internationally the group genotyped samples from over 13,000 participants, including those with psoriasis, psoriatic arthritis as well as healthy control individuals.

The research set out to learn more about what makes some people with psoriasis more at risk of developing psoriatic arthritis. This is important to be able to learn more about disease mechanisms, as well as treatment management, and ultimately preventative strategies to help improve the outcome for patients. The team also investigated the impact, if any, that the age of disease onset had.

The research set out to learn more about what makes some people with psoriasis more at risk of developing psoriatic arthritis. This is important to be able to learn more about disease mechanisms, as well as treatment management, and ultimately preventative strategies to help improve the outcome for patients. The team also investigated the impact, if any, that the age of disease onset had.

Professor Anne Barton, Musculoskeletal Theme Lead

Previously published studies have reported that genetic variants in the HLA-C gene (HLA-C*0602) have a protective effect on the development of psoriatic arthritis in patients with psoriasis. In the current study the researchers demonstrate that this effect is due to differences in the age of psoriasis onset in the psoriatic arthritis and psoriasis study groups, which leads to bias in the analysis.

When the differences in age of onset between the study groups was accounted for there was no effect of HLA-C*06:02, either protective or risk, on the development of psoriatic arthritis in patients with psoriasis. Further, after correcting for this bias an amino acid at position 97 in the protein of HLA-B was found to be a risk factor for developing PsA. This amino acid is also the major risk factor for ankylosing spondylitis, a condition that causes inflammation in the joints of the spine, leading to pain and stiffness. This finding helps explain the overlap between the two diseases.

Professor Anne Barton, Musculoskeletal Theme Lead, explained: “This study has not only identified genetic factors of developing psoriatic arthritis, but importantly identified confounding data around the age of onset which may have biased previous research into this area.

“This research saw us collaborate with colleagues in the Dermatology theme and highlights the collaborative nature of the NIHR Manchester BRC.”

Further research is needed to expand knowledge in this area and the BRC will continue to collaborate across musculoskeletal and dermatology themes in this area.

Read the paper in full in the Annals of Rheumatic Diseases

^{This research was supported by an Arthritis Research UK grant.}