Psoriatic arthritis onset in psoriatic patients receiving UV phototherapy in Italy.

Background: Psoriasis is a chronic, recurrent, and immune-mediated inflammatory disease that affects 2-3% of the world population. A substantial proportion of patients with psoriasis, approximately 40%, develop a form of inflammatory arthritis known as psoriatic arthritis (PsA), the arthritis follows the development of psoriasis, and it will develop simultaneously or possibly before the appearance of skin lesions. The presence of PsA indicates a need for more active intervention rather than purely topical therapies or UV-based therapies. The aim of this multicenter, retrospective, epidemiological study was to estimate the incidence of PsA in psoriatic patients receiving UV treatment as monotherapy.

Methods: A retrospective epidemiological study was performed in 8 dermatological reference center, located throughout Italy (2 from Northern, 3 from Center, 3 from Southern); a period of 1 year was considered. Data from the overall study population including 326 patients with a diagnosis of psoriasis were analyzed. Furthermore, data coming from follow-up visits, including screening for PsA onset through specific questionnaires were analyzed.

Results: PsA screening was positive in 27 patients (8.3%), whereas PsA diagnosis was confirmed by a rheumatologist in only 22/27 (81.5%) being therefore found in 22/326 (6.7%). Patients diagnosed with PsA had a statistically significantly higher abdominal circumference (96±15.3 vs. 88.9±18.3, P=0.048) and more commonly presented a positive past medical history for phototherapy (90.9% vs. 57.6% P=0.004).

Conclusions: Our study showed that phototherapy is not able to prevent or slow down the risk of PsA development in psoriatic patients. PsA screening should be always carried out in those patients even if asymptomatic, especially in obese subjects which are at great risk to develop PsA due to their increased systemic inflammatory state.