ROME – Patients with psoriasis were more likely to develop psoriatic arthritis if they had experienced physical trauma, based on data from a large, population-based study.
The crude incidence of psoriatic arthritis was 30 per 10,000 person-years in psoriasis patients exposed to trauma, compared with 22 per 10,000 person years in those who were not.
The hazard ratio (HR) for increased psoriatic arthritis risk with any trauma was 1.32 after adjusting for multiple factors, including patient age, gender, and the duration of psoriasis, senior study author Dr. Thorvardur Love said during a press briefing at the European Congress of Rheumatology.
“Patients with psoriasis are an easily identifiable group [to study] as they have skin disease on their body,” he noted. They also have a high risk of developing arthritis, at around 10%-30% of patients. This makes them an ideal population to study to try to find factors that might mitigate the risk and potentially have a large impact in clinical practice.
“The idea that trauma precipitates psoriatic arthritis is not new,” observed Dr. Love of Landspitali University Hospital in Reykjavik, Iceland. “It comes a little bit from the Koebner phenomenon, which is when psoriasis patients develop a new lesion in the skin where an injury has been.”
A few small studies had given rise to the idea that trauma could perhaps trigger a deep Koebner phenomenon in patients with psoriasis, and so the aim of the present analysis was to look at this idea in a larger population. Electronic health records of more than 10 million individuals living in the United Kingdom between 1995 and 2013 were analyzed from the Health Improvement Network (THIN) database. Of 70,646 patients with psoriasis who were identified, 15,416 had been exposed to some form of trauma, which was stratified as trauma involving the joints, bones, nerves, or skin.
After 425,120 person-years of follow-up, 1,010 incident cases of psoriatic arthritis had been recorded.
Having bone or joint trauma was found to increase the risk for psoriatic arthritis by 46% (HR, 1.46; 95% confidence interval, 1.13-1.54) and 50% (HR, 1.50; 95% CI. 1.19-1.90), respectively. This was after adjusting for age, gender, date of entry into the THIN database, duration of psoriasis, body mass index, smoking, alcohol consumption, and the number of visits to the general practitioner.
Neither nerve nor skin trauma were associated with an increased risk for psoriatic arthritis. Dr. Love and his fellow researchers also looked to see if patients with psoriasis had an increased risk of rheumatoid arthritis but found no significant association (HR, 1.04; 95% 0.99-1.10).
“The conclusion is that physical trauma is a risk factor for psoriatic arthritis among patients with psoriasis,” Dr. Love said. “We believe this is very important as the baseline risk is so high.”The effect is specific to psoriatic arthritis, as it is not seen in rheumatoid arthritis, which might provide clues for further research, he added. Why trauma might up the risk for developing psoriatic but not other types of inflammatory arthritis remains unclear, but the hypothesis is that patients would need to have a genetic predisposition and the “right types” of T cells in and around the joint that get disturbed in some way, perhaps by infection or by trauma. “I think it’s important to note that at this point we are not making any recommendations to the psoriasis community,” Dr. Love said. He suggested that, before any recommendations could be made, there needed to be a “really robust” conversation between patients, researchers, and physicians to determine exactly what these findings might mean. Certainly more research is needed before suggesting any lifestyle modifications that might help avoid situations associated with certain types of trauma, he said.
A literature review in the journal Clinical Rheumatology provided additional explanation of the deep Koebner effect. The investigators noted in their abstract that “the role of neuropeptides such as substance P and vasoactive intestinal peptide has been highlighted in the synovium after trauma.”
An editorial in the Journal of Rheumatology also suggested areas for additional research. Dr. Ignazio Olivieri of San Carlo Hospital in Potenza, Italy, wrote that “criteria of imputability” that should be met include “single and significant trauma; absence of joint lesion before trauma; localization of arthritis in the area of trauma; and absence or short delay between trauma and onset of arthritis.”
“You might envision treating [psoriasis] patients early [for psoriatic arthritis] if they break a leg or get a joint dislocation, but we are not there yet,” Dr. Love stressed. “This is an idea of where we could take this and where we might actually be able to have an effect.”