Background/Purpose:

Psoriasis (Ps) precedes joint inflammation by an average of 10 years psoriatic arthritis (PsA) patients. Reports have demonstrated abnormal musculoskeletal imaging findings in psoriasis patients but arthritis biomarkers have not been identified. PsA patients demonstrate increased OCP frequency in the peripheral blood. We examined the association of imaging abnormalities and OCP frequency in a longitudinal psoriasis cohort without baseline musculoskeletal symptoms.

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 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. Patients were contacted annually by phone or by a visit and those with new musculoskeletal symptoms were examined and PsA diagnosed by CASPAR criteria. Blood samples were drawn for OCP quantification from purified monocytes after 8-day cell culture.

Results:

42 Ps patients (50% female) were enrolled with a mean age 45±6 years, psoriasis duration 16±3 years, BMI 32±8 kg/m² and PASI score 8±5 and mean follow-up was 48.1±1 months. Eleven subjects had normal imaging studies (scintigraphy/MRI), 13 had active subclinical joint inflammation on imaging but 9 additional subjects, all with baseline imaging abnormalities, subsequently developed PsA. In the PsA group, 6/9 (66%) had synovitis/tenosynovitis (i.e. synovial thickening) and/or a knee effusion detected on ultrasound, compared to 5/33 (15%) in the patients without PsA. Characteristics of patients who developed PsA: 5 of 9 female, mean age 49, PASI 11.3, 5 of 9 with nail and 7 of 9 with scalp disease and mean psoriasis disease duration of 25.5 years. Active or prior enthesitis (calcification at insertions) by PDUS was noted in 9 patients without abnormal MRI or scintigraphy. Patients were categorized into 4 subsets based on the imaging analysis and/or clinical features: (1) no imaging abnormality, (Normal) n=11; (2) enthesitis or entheseal calcification, (Enthesitis), n=9; (3) sub-clinical joint inflammation, (Imaging); n=13; (4) development of PsA, (PsA) n=9. The OCP frequency was significantly different in the 4 patient subsets (P<.005) (Table 1). OCP frequency was similar in the patients who developed PsA and those with abnormal imaging findings and 3 to 4-fold higher than patients without imaging findings or enthesitis on US.

Conclusion:

Elevated OCP frequency was associated with abnormal imaging findings on scintigraphy and MRI. The combination of synovitis/tenosynovitis and/or a knee effusion on grey scale US and elevated OCP frequency identified psoriasis patients at risk for PsA.  

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