Background Nail psoriasis is acknowledged to be associated with Psoriatic Arthritis (PsA). Onycho-Psoriasis (ONPS), however, is extremely common in psoriatic population and correlate poorly with skin involvement. Further, not all clinical subsets of PsA may be linked to ONPS.
Objectives Our aim was to investigate clinical risk factors predictive for PsA in a population of psoriatic subjects.
Methods Patients were enrolled in a dermatological clinic dedicated to psoriasis care. Subjects reporting muscolo-skeletal discomfort and/or articular swelling were referred to rheumatologist. Dermatological features (PASI score, age of onset, previous/current therapies) were recorded. Rheumatological parameters encompassed joint counts (tender, swollen, damaged), entheses counts and others as suggested in the international consensus. Patients also underwent radiographic evaluation of painful areas. PsA diagnosis was established through rheumatologist opinion.
After univariate analysis for possible risk factors, a multivariate model was built for unconditional logistic regression. Statistical significance was set on P<0.01.
Results Overall, among 1200 subjects followed up at our center, 277 consecutive patients were evaluated (131 males). The mean age was 55.7 years (SD 13; median 58, range 21-81), 79.1% suffered from plaque psoriasis (41.8% had nail disease, 2.8% isolated ONPS). Median PASI score was 3.1 (IQR 1.2-5.8), 12.3% of patients had a score of 10 or more. Only 16% of patients had a previous diagnosis of PsA.
We diagnosed 110 PsA, 59.1% of whom as consequence of enrolment. PsA was early (onset within 1 year since enrolment) in 33.6%.
PsA was classified in 82.7% of cases as peripheral arthritis, 34.5% of patients had dactylitis and 15.5% showed axial disease. Radiographic damage due to PsA was present in 38.2% of cases.
At univariate level, risk factors for PsA were: male sex; younger age at enrolment and at psoriasis onset. The multivariate analysis (shown in table 1) confirmed statistical significance only for male sex, although at low level (95% CI 1.3-3.9).
Conclusions PsA seems to be hardly linkable to clinical parameters easily available in daily dermatological practice. Above all, our data alert for the first time that the mere presence of nail psoriasis does not confer increased risk for PsA.
Disclosure of Interest None Declared