Study Links Psoriasis to Higher Psoriatic Arthritis Risk

New research finds the incidence of psoriatic arthritis (PsA) among patients with psoriasis is much greater than previously thought.

In an effort to explain the incidence and risk factors for PsA, a team of investigators studied a total of 464 patients, following enrollees in the Toronto Psoriasis Cohort for an 8-year period, with their current analysis focusing on those without arthritis at baseline. The mean age at the time of enrollment was 47, with a mean duration time of psoriasis of 16 years. In three-quarters of patients, psoriasis onset occurred before the age of 40.
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All members of the cohort had dermatologist-confirmed psoriasis, but no present or past inflammatory arthritis or spondyloarthropathy. Among the 464 patients taking part in the study, there were 51 cases of incident PsA being confirmed by a rheumatologist over a mean follow-up period of 4.1 years per patient. At each annual assessment, musculoskeletal examinations detected the presence of joint swelling and tenderness, along with dactylitis and enthesitis. Imaging analyses also documented joint damage.

In the overall cohort, the Psoriasis Area and Severity Index (PASI) was below 10 in nearly 87%, but higher than 20 in 2.4%, according to the authors. In the PsA subgroup, 6.7% were among those with the highest scores. Arthritis was peripheral in 64.7% of PsA patients. Arthritis was axial in 17.6% of patients in that group, both peripheral and axial in 15.7%, and enthesitis was present in 2% of this cohort.

Overall, the annual incidence of PsA was 2.7% per 100, according to the investigators, who point out that earlier research found a cumulative incidence of just 5.1% 20 years after the onset of psoriasis.

These findings “demonstrate that patients with psoriasis are at high risk of developing psoriatic arthritis,” says Dafna Gladman, MD, FRCPC, a professor of medicine at the University of Toronto, and a co-author of the study.

“The incidence is much higher than previously thought, and the risk is linear, which means practitioners need to ask their patients with psoriasis if they have any joint pain or back pain with stiffness on a regular basis, not just at presentation,” adds Gladman.

While there are some items which have been identified as risk factors, “it is probably best to ask all patients about joint symptoms,” says Gladman, noting that the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) is currently working on developing criteria for inflammatory musculoskeletal disease, “which should help non-experts in at least screening for this condition.”

—Mark McGraw

Reference

Eder L, Haddad A, et al. the incidence and risk factors for psoriatic arthritis in patients with psoriasis - a prospective cohort study. Arthritis & Rheumatology. 2015.