Objective: To assess the evolution of disease subgroups and the frequency of progression of peripheral joint disease in a prospectively studied cohort of patients with psoriatic arthritis (PsA).
Methods: The cohort was identified as the first consecutive 100 patients attending a psoriatic arthritis clinic and who had been the subject of a previously published cross-sectional retrospective study. Nine of the 100 patients had died, three declined follow-up and one could not be traced. The remaining 87 patients (49 females, 38 males) completed the study proforma at a median follow-up interval of 65 months (range 39-90). An analysis of initial plasma viscosity compared with rates of progression of joint score was performed.
Results: Eighteen patients changed subgroup; 11 had an increase in the number of joints involved, six a decrease, and one changed from an oligoarticular pattern to predominant spondylitis. Within the polyarticular group 37/51 patients had an increase in the number of joints involved. For the whole population, there were significant increases in the number of joints involved (median 6 vs 11, P < 0.001 Wilcoxon signed rank) and Health Assessment Questionnaire scores (median 0.375 vs 0.5, P < 0.001). The median rate of joint progression was 0.42 peripheral joints per year (range 0-7.2). However, the rate of peripheral joint involvement was highest in the first year of arthritis (median 4.0 joints/yr) as measured in 13 patients who had onset within 12 months of baseline assessment. There were no significant differences in skin and nail scores although nine more patients had developed nail disease. There was a significant correlation between the initial viscosity and rate of progression of joint damage (Spearman correlation, P < 0.011).
Conclusions: Peripheral joint disease is progressive in the majority of patients with PsA and reinforces the need for effective monitoring and treatment.