Background/Purpose:

Psoriasis (Ps) precedes joint inflammation by about 10 years in patients who develop psoriatic arthritis (PsA). Several studies have documented abnormal musculoskeletal imaging findings and we found elevated osteoclast precursor (OCP) frequency in Ps patients without musculoskeletal signs or symptoms. The association of imaging abnormalities and OCP frequency with arthritis onset in a prospective psoriasis cohort, however, has not been examined.

Methods:

Ps patients with > 5 years of psoriasis or >10% body surface area (any disease duration) were enrolled if they scored less than 36 on the Psoriatic Arthritis Screening and Evaluation (PASE) questionnaire and showed no active arthritis or enthesitis on rheumatologic exam. All patients were imaged with a 3-phase bone scan and Power Doppler Ultrasound (PDUS) of joints and entheses. If the bone scan revealed evidence of inflammation, a gadolinium enhanced 3T MRI was performed on the joint with the highest scintigraphy signal. All imaging studies were analyzed by 2 radiologists. A diagnosis of PsA was confirmed by the CASPAR criteria on follow-up annual exams. Blood samples were drawn for OCP quantification after 8-day cell culture.

Results:

39 Ps patients (44% female) were enrolled with a mean age 45±6 years, disease duration 15±2 years, BMI 30±3 kg/m² and PASI score 9±2. Eleven subjects had normal studies, 8 had active joint inflammation on imaging but remained asymptomatic but 5 additional subjects with baseline imaging abnormalities subsequently developed PsA. Thirteen patients showed evidence of active or prior enthesitis (calcification at insertions) on imaging. Two patients had active tenosynovitis and 1 patient had plantar fasciitis. The patients were categorized into 4 subsets based on the imaging analysis and/or clinical features: (1) no imaging abnormality, n=11; (2) joint inflammation (imaging) without clinical symptoms, n=8; (3) development of PsA, n=5; (4) enthesitis or entheseal calcification, n=13. The OCP frequency was examined in cultured PBMC or purified monocytes isolated from these 4 patient subsets (Table 1).

	(1) Normal	(2) Imaging Arthritis	(3) PsA	(4) Enthesitis
PBMC	9 ± 9.3	140 ± 141	316± 267	64 ± 49
Monocytes	168 ± 96	1,209± 492	1,273± 549	467 ± 231

Table 1. OCP frequency in 4 cohorts of Ps patients categorized by imaging results (mean+SEM).

Conclusion:

Among 39 Ps patients monitored for 3 months to 3 years, 8 patients showed baseline imaging abnormalities but remained asymptomatic; 5 patients with imaging abnormalities subsequently developed PsA, and 13 patients had acute or chronic entheseal signals. The OCP frequency was highest in patients with new onset PsA and inflammation on imaging studies. These results demonstrate the high prevalence of subclinical joint inflammation and entheseal changes in Ps and provide evidence that elevated OCP frequency may serve as a surrogate marker for joint inflammation and risk for arthritis in Ps patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/abnormal-imaging-and-increased-osteoclast-precursors-in-a-psoriasis-cohort-are-associated-with-new-onset-of-psoriatic-arthritis/