Over Half of Psoriatic Arthritis Patients Previously Diagnosed with Psoriasis

Paras Karmacharya, MD

A new population-based study found that over half of patients with psoriatic arthritis (PsA) had previously been diagnosed with psoriasis while the remaining patient had concurrent psoriasis with PsA.

Investigators noted that psoriasis often precedes psoriatic arthritis, with up to 30% of patients with psoriasis eventually developing inflammatory synovio-entheseal (SE) inflammation. As such, this sequence allows doctors to identify PsA earlier in the disease course.

Despite this, some studies have shown that the time to transition from psoriasis to PsA had not been fully explained by genetic factors alone.

In the current study, investigators led by Paras Karmacharya, MD, Division of Rheumatology at the Mayo Clinic in Rochester, Minnesota, identified demographic and clinical characteristics associated with a longer time from psoriasis to PsA compared to a concurrent diagnosis.

The Methods

The retrospective nested case-control study was performed using resources from the Rochester Epidemiology Project (REP).

Investigators believed that the population of Olmsted County, which comprised part of the city of Rochester, was suited for investigation of the epidemiology of PsA. Additionally, comprehensive medical records for all residents seeking medical for over 5 decades were available.

A retrospective, population-based cohort of incident PsA patients 18 years and older from Olmsted County were identified.

From there, PsA patients were divided into 2 groups including patients with concurrent psoriasis and PsA within 1 year and patients with psoriasis before PsA in less than 1 full year.

Patients with PsA prior to psoriasis were excluded, and age- and sex-adjusted logistic regression models were used to examine factors associated with the time between psoriasis and PsA diagnosis.

The Findings

Karmacharya and colleagues identified a total of 164 patients with incident PsA between January 1, 2000 and December 31, 2017. Among those patients, 158 had a current or personal history of psoriasis. The mean (SD) age at PsA diagnosis was 46.3 (12) years, and 46% of patients were female.

Investigators observed that the median (interquartile range) time from psoriasis to PsA was 35.5 (0.8-153.4) months.

A total of 64 patients (41%) patients had concurrent psoriasis and PsA while 94 (59%) had onset of psoriasis before PsA.

Additionally, the estimated age at onset of psoriasis symptom (OR per 10-year decrease = 1.63, 95% CI: 1.26-2.11) and psoriasis severity (OR = 3.65, 95% CI: 1.18-11.32 for severe vs. mild) were associated with having a psoriasis diagnosis more than 1 year prior to incident PsA.

“In this population-based study, approximately 60% of the patients had psoriasis before PsA, and the rest had concurrent psoriasis and PsA,” the team wrote. “Patients with lower age at psoriasis onset or severe psoriasis were more likely to have a longer time to transition from psoriasis to PsA.”

The study, "Time to transition from psoriasis to psoriatic arthritis: A population-based study," was published online in Science Direct.