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19-05-2011 | Psoriasis | Article

Psoriatic arthritis may be more common than previously reported


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MedWire News: There may be a higher incidence of psoriatic arthritis among patients with moderate-to-severe psoriasis than has been previously reported, show the results of Canadian research.

While other studies have suggested a cumulative incidence of psoriatic arthritis of 3.1% at 10 years after initial psoriasis onset, the current findings indicate a rate of between 3.2% and 4.0% per year.

Dafna Gladman (University of Toronto Psoriatic Arthritis Clinic, Ontario) and colleagues say they are among the first to prospectively study psoriatic arthritis incidence, which is usually observed retrospectively, and in the general population.

"There is limited information about the incidence of psoriatic arthritis among psoriasis patients," they write in the journal Arthritis Care and Research.

Thus the team followed-up 313 moderate-severe psoriasis patients recruited between 2006 and 2008 for a mean 1.71 years per person (534.5 years in total), of whom 253 had at least 1 year of follow-up data available. A total of 10 patients were diagnosed with psoriatic arthritis during the study period using the Classification Criteria for Psoriatic Arthritis.

Those who received an arthritis diagnosis were aged a mean 52.2 years at onset, four were men, six had a family history of psoriasis, and none had a family history of psoriatic arthritis. The mean number of inflamed joints among these patients was three.

This gave an annual incidence rate of 1.87 cases overall per 100 patients (3.2%) in the whole cohort, and a rate of 2.53 per 100 patients (4.0%) when only patients with at least 1 year of follow-up were included.

Both of these rates are higher than those previously reported, note Gladman et al.

Among those who did develop the condition, the duration between study enrollment and development of psoriatic arthritis ranged from 4 to 42 months, with 3 out of 10 patients diagnosed within the first year.

The researchers note that most of the patients had oligoarthritis at the time of psoriatic arthritis diagnosis and that only a few had developed clinical or radiographic joint damage, "which indicates an early diagnosis of the disease.

"We cannot predict the course of these patients with mild forms of arthritis, although our previous studies suggest that male patients with a smaller number of involved joints fare better," they conclude.

MedWire ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2011

By Sarah Guy

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