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Clinicians treating patients with psoriasis should be on the lookout for certain signs that joint involvement is likely to develop, according to a from the European Alliance of Associations for Rheumatology (EULAR).

In particular, psoriasis patients showing persistent pain and imaging abnormalities in the joints are at heightened risk for progressing to psoriatic arthritis (PsA), reported a EULAR task force led by Dennis McGonagle, MBChB, PhD, of the University of Leeds in England.

These are in addition to traditional risk factors for progression, such as family history, obesity, very extensive psoriatic lesions, and nail involvement, the group indicated. Patients showing these signs should be told about their heightened risk for PsA and urged to report new or increasing symptoms promptly, while doctors should reassess patients' risk factors periodically.

Not only clinicians can benefit from the new document, the authors suggested: it could also be used to establish inclusion criteria for trials testing novel methods to prevent psoriasis-to-PsA progression. Up until now, they noted, "data in this space are limited with the field being controversial with a lack of established serological markers and a standardised working definition for early phase PsA for PsA prevention studies."

Around three out of every 10 psoriasis patients eventually develop enough arthritic features to meet criteria for PsA. That poses a problem insofar as "incomplete understanding of the immunogenetic and other factors linked to disease evolution" means that it's not possible to identify which three will progress to PsA, McGonagle and colleagues explained.

EULAR leaders commenced the effort to bring some unanimity to the concept of "early PsA" in early 2021, with a 30-member task force. Most were rheumatologists, with five dermatologists included as well. Other members included specialists in methodology and patient research and a non-physician healthcare professional.

The group sought to categorize PsA into three stages of development: psoriasis with heightened risk, "subclinical PsA," and full-blown clinical PsA. They did not attempt to set formal criteria, but rather to establish a foundation for research to flesh them out, especially for the first two designations. Clinical PsA is already well defined, of course, but the task force believed it would be useful to consider how to characterize new-onset clinical PsA as an endpoint for prevention trials.

In the end, they decided that clear development of clinical synovitis in a person with psoriasis would serve as such an endpoint -- stressing, however, that synovitis may be transient, and thus this definition would not be appropriate in a routine practice setting.

Specific Points to Consider

McGonagle and colleagues emphasized that clinicians must take other potential diagnoses or comorbidities -- e.g., osteoarthritis or fibromyalgia -- into account when a patient complains of joint pain. The group also noted that the connection between joint pain in psoriasis patients and incipient PsA is ripe for research. Many questions remain unanswered, such as whether the site or duration of pain matter in terms of risk for PsA development.

Clinicians should ask their psoriasis patients regularly about musculoskeletal pain or functional limitations at regular visits, the task force recommended. And patients with such complaints may merit imaging (including ultrasound, MRI scans, or both in addition to standard x-rays) to look for "synovio-entheseal involvement/abnormality."

Notably, however, imaging abnormalities in the absence of symptoms are not themselves indicative of increased PsA risk. If found, they "should be considered carefully in order to avoid the risk of inappropriate treatment," the group wrote. "Subclinical findings detected by imaging can be present in the subclinical PsA phase but there is no evidence that this should favour specific therapeutic choices in the management of people with [psoriasis] without musculoskeletal symptoms or be sufficient for the diagnosis of PsA."

On the other hand, symptoms plus imaging abnormalities may at least be considered sufficient to qualify patients for clinical prevention trials.

One major issue that needs more research is whether disease-modifying treatments for psoriasis, particularly biologic drugs, affect risk of progression to PsA. McGonagle and colleagues found evidence going both ways: some studies indicated that such treatment reduced the risk, while at least one has suggested the opposite. For now, the group concluded that the evidence favors "the use of treatment that could ameliorate both skin and joint manifestations" in patients with risk factors for arthritic progression.

Overall, the group concluded, "these findings set the scene for both PsA as an outcome in prevention studies and the regression of arthralgia and imaging abnormalities as bespoke strategy relevant to PsA cases, many of whom require chronic therapy for cutaneous [psoriasis]."

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