Late onset psoriatic arthritis in a longitudinal cohort: Disease presentation, activity over time and prognosis.

Aims: To evaluate disease activity of late onset psoriatic arthritis (LoPsA) patients at presentation, during follow-up, and after 5years of follow-up, compared to young onset PsA patients (YoPsA).

Methods: The study included patients with PsA followed prospectively within 2years from diagnosis. Patients were divided into two groups: (1) LoPsA - defined as disease onset ≥ 50 years, (2) YoPsA - defined as disease onset < 50 years. Descriptive statistics are provided and multivariable logistic regression models were developed to compare these groups.

Results: Five hundred and sixty-six patients were included at presentation. Regression analysis showed that the LoPsA group at presentation was characterized by: less males (OR 0.4, p = 0.001), less HLA-C*06 (OR 0.3, p = 0.005), longer psoriasis duration (OR 1.04, p = 0.0005), higher BMI (OR 1.1, p = 0.005) and higher modified Steinbrocker score (mSS) (OR 1.1, p = 0.005). Regression analysis adjusted for gender, BMI, psoriasis duration, HLA and treatments after 5years of follow-up revealed a trend toward higher adjusted mean active joint count (OR 7.98, p = 0.052) and higher mean mSS score (OR 13.39, p = 0.007) in the LoSpA group compared to the YoPsA group. During 5years of follow-up, the YoPsA patients were treated with more NSAIDs (96% vs. 88%, p = 0.04), while there were no significant differences in the DMARDs and biologic drugs.

Conclusion: The LoPsA patients at presentation are characterized by female predominance, higher BMI, more damage and less HLA-C*06. After 5years of follow-up the LoPsA patients have worse prognosis manifested by a trend toward higher disease activity burden and significantly more damage.