A polyarticular onset predicts erosive and deforming disease in psoriatic arthritis

Objectives: To analyse the factors predicting erosive-deforming arthropathy in patients with psoriatic arthritis (PsA). Methods: A prospective cohort study was undertaken with 71 patients diagnosed as having PsA (44 men and 27 women, mean age 47 (SD 12) years). At the recruitment period patients had disease without evidence of radiological damage. Patients were studied and followed up according to a standard protocol from January 1991 to June 2001. Erosive and deforming disease was defined by the presence of erosions, joint space narrowing, subluxation, and/or ankylosis of peripheral joints. Univariate and multivariate analyses were performed to evaluate factors predicting erosive and deforming disease. Results: At the end of the study 32 of 71 (45%) patients had developed erosive and deforming disease. Among them, 18 of 32 (56%) had a polyarticular onset, two of 32 (6%) showed a distal interphalangeal joint disease onset, six of 32 (19%) presented with oligoarthritis, and six of 32 (19%) presented with axial disease as the form of disease onset (p=0.001). Mean time to detect erosions or joint space narrowing was 20 (SD 4) months. Men showed fewer erosions than women (p=0.05). Patients who carried the HLA-B27 antigen showed less erosive disease than patients who lacked it (p=0.05). Patients with erosive and deforming disease had poorer functional performance than those without it as measured with the Health Assessment Questionnaire (HAQ) and the American College of Rheumatology (ACR) criteria (p<0.05 with both measurements). In multivariate analysis, only a polyarticular onset remained as an indicator of erosive and deforming disease (odds ratio (OR) 37, 95% confidence interval (95% CI) 3.6 to 88, p=0.025). Conclusions: A polyarticular onset (five or more swollen joints) of PsA was the unique independent risk factor which predicted the appearance of erosive and deforming disease over time. These data may be useful for clinicians treating patients with PsA, as it may guide treatment towards a more aggressive and earlier intervention.