RESEARCH - Polyarticular psoriatic arthritis is more like oligoarticular psoratic arthritis than RA

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ls of the Rheumatic Diseases 2007;66:113-117

© 2007 by BMJ Publishing Group Ltd & European League Against Rheumatism

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EXTENDED REPORT

Polyarticular psoriatic arthritis is more like oligoarticular psoriatic

arthritis, than rheumatoid arthritis

P S Helliwell1, G Porter2, W J 3 for The CASPAR Study Group*

1 Academic Unit of Musculoskeletal and Rehabilitation Medicine, University

of Leeds, Leeds, UK

2 Airedale NHS Trust, West Yorkshire, UK

3 Rehabilitation Teaching and Research Unit, Department of Medicine,

Wellington School of Medicine and Health Sciences, University of Otago,

Wellington, New Zealand

Background and objective: Since the original description of psoriatic

arthritis (PsA) subgroups by Moll and , there has been some

discrepancy in the precise prevalence of the different subgroups and in

particular the proportion of patients with polyarthritis. The higher

prevalence of the polyarthritis subgroup may be due to the inclusion of

patients with seronegative rheumatoid arthritis with coincidental psoriasis.

The classification of psoriatic arthritis (CASPAR) study database provided

an opportunity to examine this question.

Methods: The CASPAR study collected clinical, radiological and laboratory

data on 588 patients with physician-diagnosed PsA and 525 controls with

other inflammatory arthritis, 70% of whom had rheumatoid arthritis. Patients

with PsA were divided into two groups: polyarthritis and non-polyarthritis

(which included the Moll and subgroups of spinal disease, distal

interphalangeal predominant and arthritis mutilans) and were compared with

patients with rheumatoid arthritis. Comparisons were made between all three

groups and, if a significant difference occurred, between the two groups

with PsA.

Results: The three groups differed significantly with regard to all clinical

and laboratory variables except duration of disease. Significant differences

were also found between the two groups of PsA in terms of age, sex, total

number of involved joints, disability score and symmetry. However, no

differences were found between the groups of patients with PsA in terms of

seropositivity for rheumatoid factor and antibodies to cyclic citrullinated

peptide, enthesitis, and spinal pain and stiffness. Further, dactylitis was

commonly seen in patients with PsA (57% in the polyarticular group and 45%

in non-polyarticular group), and uncommonly found in patients with

rheumatoid arthritis (5%). With the exception of entheseal changes,

syndesmophytes and osteolysis, typical radiological features of PsA could

not be used to distinguish between the PsA subgroups.

Conclusions: The evidence suggests that the changing prevalence of the

polyarticular subgroup of PsA is not because doctors include patients with

seronegative rheumatoid arthritis with coincidental psoriasis.

http://ard.bmj.com/cgi/content/abstract/66/1/113?etoc

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