Joint Pain and Synovitis Linked to Increased Psoriatic Arthritis Risk in Patients with Psoriasis

A new trial of magnetic resonance imaging (MRI) finds that analyzing scans for subclinical signs of inflammatory joint disease can help predict which psoriasis patients will go on to develop psoriatic arthritis.

Investigators performed high-field MRI scans on 55 patients with psoriasis (but not psoriatic arthritis) and another 30 healthy controls. They then scored each scan for synovitis, osteitis, tenosynovitis and periarticular inflammation according to the psoriatic arthritis magnetic resonance imaging scoring (PsAMRIS) method. Psoriasis patients also received complete clinical evaluations, high-resolution peripheral quantitative computerized tomography (CT) scans (which were used to find erosions and enthesiophytes) and at least 1 year of follow up.

At baseline, 47% of all psoriasis patients had at least 1 inflammatory lesion that was visible on the initial MRI scan. The most common inflammatory lesion was synovitis (which was found in 38% of the psoriasis patients), followed by osteitis (11%), tenosynovitis (4%) and periarticular inflammation (4%). The mean PsAMRIS synovitis score was 3.0 units (± a standard deviation of 2.5 units).

Results on these initial MRI scans were strongly associated with each psoriasis patient’s risk of developing psoriatic arthritis. Some 60% of the patients with subclinical synovitis and symptoms related to arthralgia — but only 13% of patients who began with normal MRI results and no reported arthralgia — went on to be diagnosed with psoriatic arthritis at some point during the follow-up period.

The results of baseline CT scans, however, were unrelated to the results from baseline MRI scans. Patients found to have inflammatory lesions on MRI scans were not significantly more or less likely than patients with normal MRI results to have bone erosions or enthesiophytes.

“Prevalence of subclinical inflammatory lesions is high in patients with cutaneous psoriasis,” the study authors wrote in the Annals of Rheumatic Diseases. “Arthralgia in conjunction with MRI synovitis constitutes a high-risk constellation for the development of psoriatic arthritis.”

A number of prior studies have tried to find factors that predict which psoriasis patients will go on to develop psoriatic arthritis, according to a 2010 research review that appeared in Psoriasis Forum, but even very basic questions remain unanswered. Estimates from large epidemiologic studies of the percentage of psoriasis patients who also suffer from psoriatic arthritis range from 7 to 26.

That said, there is strong evidence that a number of easily identified factors can help predict which psoriasis patients will later be diagnosed with psoriatic arthritis.

At least 4 large cohort studies have found significant correlations between psoriasis severity and the risk of psoriatic arthritis. A study from Minnesota, for example, reported that patients whose psoriasis affected 3 or more areas of their bodies faced more than twice risk of other psoriasis patients of developing psoriatic arthritis.

Additional risk factors identified by the research review include patient genetics (1 study found 48.8 times the normal risk of psoriatic arthritis if a first-degree relative has the disease) and the presence of particular psoriasis symptoms such as scalp lesions, nail changes or peripheral joint involvement.

“The physical examination is an important step when assessing for risk of psoriatic arthritis. Nail dystrophy and dactylitis are high-yield risk factors for psoriatic arthritis because the presence of either of these in a psoriasis patient with inflammatory arthritis qualifies the patient for a diagnosis of psoriatic arthritis according to the CASPAR [Classification of Psoriatic Arthritis] criteria,” the review authors wrote. “It is intriguing that the location of a patient’s psoriasis might also influence risk of psoriatic arthritis, with scalp, intergluteal, or perianal lesions conferring higher risk.”