Objective: To determine whether the presence of psoriasis influences the presentation and early outcome of disease in a primary case based inception cohort of patients with early inflammatory polyarthritis.
Methods: In total, 966 patients with early inflammatory polyarthritis referred to the Norfolk Arthritis Register were studied. The clinical and demographic variables of patients with and without psoriasis were compared.
Results: Fifty-one patients (5.3%) had psoriasis on examination. Compared to other patients with inflammatory polyarthritis, those with psoriasis were significantly more likely to be male (49 vs 34%) and less likely to be seropositive for rheumatoid factor (RF) (13 vs 31%). The pattern of joint involvement was similar, as was the outcome at one year. Fewer patients with psoriasis developed radiological erosions (22 vs 39%). Multivariate analysis suggested that this was due to RF acting as a confounder.
Conclusion: Among patients with early inflammatory polyarthritis there are few strong differences between patients with and without psoriasis, some of which may be accounted for by the absence of RF.