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Psoriatic Arthritis

(see also: Spondyloarthropathies)

Discussion

  • psoriasis affects 1-2 % of U.S. population & typically presents w/ well-defined erythematous scaly plaques;
  • only a minority of pts with psoriasis develop arthritis;
  • when arthritis develops, it most often is an asymmetrical oligoarthritis, which at times may be quite destructive;
  • some patients may develop spondylitis (usually will have HLA-B27 antigen);
  • incidence of MV prolapse is high ( > 50%);

Clinical Presentation

  • clinical course of psoriasis is long-term, w/ characteristic relapses & remissions;
  • age: presents in 3rd-4th decade;
  • gender: men and women are affected in equal numbers;

skin

  • circumscribed erythrematous maculopapules or silver scaling;
  • activity of skin lesions may or may not correlate w/ of peripheral arthritis;
  • skin lesions may appear similar to Reiter's Syndrome;
  • subcutaneous nodules are absent;
  • nail deformities: 80% of patients will have nail lesions, including nail pits and onycholysis;

joints

  • involves the small joints of feet and hands more than any other joint;
  • dactylitis may involve degree of tenosynovitis as well;
  • severe cases may progress to arthritis mutilans, w/ widespread destruction;

foot

  • calcaneal spurs, sclerosis, & periarticular erosions of MP joints;
  • spontaneous fusions do not occur;

hand & wrist

  • may have fusiform swelling of digits & nail changes;
  • asymmetric joint involvement which affects terminal IP joints;
  • DIP joint involvement.
  • marked tendency for hand joints to becomes stiff;
  • MP joints: become stiff in extension, rather than stiff in flexion as in RA;

Radiographic Features

  • cartilage loss & erosions resemble changes seen in RA;

IP Joints

  • symmetrical bony involvement with a predilection for DIP joints;
  • erosive damage in the IP joints (presence of pencil-in-cup change);
  • jonit destruction, widened joint spaces, & well defined adjacent bony surfaces;
  • advanced cases reveal a "pencil in cup" deformity, tuft resorption, and eventual ankylosis;
  • interphalangeal joint of the great toe is often involved;
  • there is generally a lack of juxta-articular osteopenia;
  • erosions are often para-marginal (where as in RA erosions are marginal);

Spine & SI Joint

  • beaklike nonmarginal syndesmophytes are found (also seen in Reiter's);
  • bilateral sacroilitis occurs in 10-30% of pts;
  • paraspinal ligamentous calcification or ossification may occur similar to AS;

Labs

  • RF & antinuclear AB test (ANA) are neg;

Treatment

  • non-steroidals and occasionally methotrexate or oral colchicine;
  • sulfasalazine 1-2 gm per day has excellent efficacy;
  • systemic steroids should be used with caution since these may cause skin lesions to become pustular;
  • topical treatments:
    • anthralin, corticosteroids, keratolytic agents;
  • DIP joints are frequently spontaneously fused;
  • nail deformity:
    • w/ pitting, longitudinal ridging, consider intralesional corticosteroids;
    • triamcinolone acetonide 5 mg/ml injected into nail fold q3-4 weeks;
  • postoperative infection rates are higher than seen w/ RA

References