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Clinical, radiological, and functional assessment in psoriatic arthritis: is it different from other inflammatory joint diseases?
  1. D D Gladman
  1. Correspondence to:
    Dr D D Gladman
    Centre for Prognosis Studies in the Rheumatic Diseases, Toronto Western Hospital, 399 Bathurst Street, 1E 410B, Toronto, Ontario, M5T 2S8, Canada; dafna.gladman{at}

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Psoriatic arthritis (PsA) is an inflammatory arthritis associated with psoriasis.1 It is usually seronegative for rheumatoid factor. PsA may affect as many as 30% of patients with psoriasis. It may present in one of a number of clinical patterns, including:

  • a distal pattern affecting the distal interphalangeal (DIP) joints of the hands and feet

  • an oligoarticular pattern in which four or fewer joints are affected, usually in an asymmetric distribution

  • a polyarticular pattern which may be indistinguishable from rheumatoid arthritis

  • a predominantly spinal pattern

  • arthritis mutilans, a very destructive form of arthritis.

PsA affects men and women equally, and usually begins in the fourth decade. Although the psoriasis precedes the arthritis in the majority of patients, some 15% of patients have simultaneous development of skin and joint disease, and in another 15% the joint manifestations may precede the skin lesions. Because of its asymmetrical nature, the occurrence of spondylitis in about 50% of the patients, its extra-articular features, and its association with human leucocyte antigen (HLA)-B*27, PsA has been classified among the seronegative spondyloarthropathy (SpA) group of conditions.


PsA presents with a peripheral arthritis, and thus needs to be distinguished from rheumatoid arthritis (RA). In addition, since more than 50% of patients with PsA have DIP joint involvement, it needs to be distinguished from osteoarthritis (OA). As many patients with PsA have elevated serum uric acid, PsA needs to be differentiated from gout. As a member of the SpA group, it needs to be differentiated from the other members of the group namely ankylosing spondylitis (AS), reactive arthritis, …

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