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.
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.
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.
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.