Background/Purpose: We have previously reported that the presence of musculoskeletal pain in psoriasis patients is associated with a higher risk of developing psoriatic arthritis (PsA) (1). Furthermore, a subset of psoriasis patients shows evidence for structural entheseal lesions (SEL) in their hand joints (2), sometimes also referred as “Deep Koebner Phenomenon”, which are highly specific for psoriatic disease and virtually absent in healthy controls, rheumatoid arthritis and hand osteoarthritis patients (2-4). However, it remains unclear whether SEL alone or in combination with musculoskeletal pain are associated with the development of PsA. Therefore, we aimed to test whether the presence of SEL in psoriasis patients increases the risk for progression to PsA and how this is related to the presence of musculoskeletal pain.

Methods: Psoriasis patients without evidence of PsA were enrolled in a prospective cohort study between 2011 and 2018. All patients underwent baseline assessment of SEL in their 2^nd and 3^rd MCP joints by high-resolution peripheral quantitative computed tomography (HR-pQCT). The risk of PsA development associated with SEL and arthralgia was explored using survival analyses and multivariable Cox regression models.

Results: 114 psoriasis patients (72 men/42 women) with a mean (SD) follow-up duration of 28.2 (17.7) months were included, 24 of whom developed PsA (9.7 /100 patient-years, 95%CI 6.2 to 14.5) during the observation period. Patients with SEL (N=41) were at higher risk of developing PsA compared to patients without such lesions (21.4/100 patient-years, 95%CI 12.5 to 34.3, HR 5.10, 95%CI 1.53 to 16.99, p=0.008) (Kaplan Meier plot A). Furthermore, while patients without arthralgia and without SEL had a very low progression rate to PsA (1/29; 3.4%), patients with arthralgia but no SEL showed higher progression (5/33; 15.2%), which was in line with previous observations (1) (Kaplan Meier plot B). Presence of SEL further enhanced the risk for progression to PsA both in the absence (6/16; 37.5%) and presence (6/14; 42.8%) of arthralgia with the highest progression rate in those subjects with both arthralgia and SEL (p< 0.001 by log rank test for trend) (Kaplan Meier plot B).

Conclusion: Presence of SEL is associated with an increased risk of developing PsA in patients with psoriasis. If used together with pain, SEL allow defining subsets of psoriasis patients with very low and very high risk to develop PsA.

References:

(1) Faustini F et al. Ann Rheum Dis. 2016;75:2068-2074

(2) Simon D et al. Ann Rheum Dis. 2016;75:660-6

(3) Finzel S et al. Ann Rheum Dis. 2011;70:122-7

(4) Finzel S et al. Arthritis Rheum. 2011;63:1231-6

(A) Kaplan-Meier plots of psoriatic arthritis-free survival by presence/absence of structural entheseal lesions (SEL) at baseline. P value by log-rank test;, (B) Kaplan-Meier plots of psoriatic arthritis-free survival by four groups; 1, no arthralgia and no SEL at baseline; 2, arthralgia but no SEL (Arthralgia only) ; 3, no arthralgia but SEL(SEL only) ; 4, arthralgia and SEL

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/structural-entheseal-lesions-in-psoriasis-patients-are-associated-with-an-increased-risk-ofprogression-to-psoriatic-arthritis-a-prospective-cohort-study/