Age at disease onset may help to further characterize the disease phenotype in psoriatic arthritis.

Objective: To evaluate whether the age of disease presentation helps to better characterize the disease phenotype in PsA.

Methods: Retrospective cohort study that included 205 consecutive patients fulfilling the CASPAR criteria for PsA. Study outcomes were assessed using univariate and multivariate analyses according to the age of onset of both skin and joint disease (cut off at 40years).

Results: Early onset psoriasis (EOP) showed more extensive skin involvement (OR 2.3, P=0.011), axial pattern as disease onset (OR 4.6, P=0.009) and mixed pattern during evolution (OR 2.4, P=0.019), family history of both psoriasis (OR 3.1, P=0.003) and PsA (OR 4.0, P=0.021), higher prevalence of HLA-C*06 (OR 2.03, P=0.03) and HLA-B*27 (OR 2.7, P=0.02). Early onset arthritis (EOA) had more family history of PsA (OR 2.9, P=0.007), and HLA-B*27 positivity (OR 5.9, P<0.0001). Patients with late onset arthritis (LOA) were more likely to have DM (OR 4.0, P=0.009), hypertension (OR 2.5, P=0.004), dyslipidemia (OR 2.3, P=0.011), and obesity (OR 1.7, P=0.012). Late onset psoriasis (LOP) tended to have more obesity (OR 1.9, P=0.035), DM (OR 9.4, P<0.0001), hypertension (OR 4.1, P<0.0001), and ischemic heart disease during follow-up (OR 5.9, P=0.021). In multivariate analysis, LOP predicted DM development (OR 12.1, P=0.006). LOA was shown to be an independent risk factor for hypertension (OR 5.2, P=0.039).

Conclusion: Age at disease onset exerts a strong influence on several domains of disease phenotype in PsA. Therefore, this descriptor should be considered a good stratification option for epidemiological and genetic studies in PsA.