Arthritis, Psoriatic

Basics

A chronic, destructive, seronegative arthropathy in patients with long-standing psoriasis

Description

  • Psoriatic arthritis (PsA) is a seronegative spondyloarthropathy characterized by inflammatory arthritis and enthesitis.
  • Five patterns of arthritis in PsA:
    • Asymmetric oligoarthritis: <5 joints
    • Distal interphalangeal (DIP) joint predominant: osteoarthritis-like, associated with nail psoriasis
    • Symmetric polyarthritis: may be indistinguishable from rheumatoid arthritis (RA)—typically milder
    • Spondyloarthritis: asymmetric and discontinuous, unlike ankylosing spondylitis (AS)
    • Arthritis mutilans: destructive, resorptive arthritis; produces “opera-glass” or “telescoping” digit
  • Psoriasis may be limited in extent.
    • Course of arthritis and extent of psoriasis do not correlate.
    • Other extra-articular features, such as iritis, are less common.
    • Damaging joint disease may occur in 40–60%. Characteristic radiologic changes include “pencil-in-cup” deformity and periostitis.
  • Rheumatoid factor (RF) and anti–cyclic citrullinated peptide (anti-CCP) antibody are usually negative. HLA-B27 may be positive.

Epidemiology

  • Peak onset age: 30 to 50 years
  • Predominant gender: female = male
  • Polyarthritis is more common in women.
  • Spondylitis in up to 25%, more common in males
  • Psoriasis precedes arthritis in most patients by an average of 12 years. Arthritis preceding psoriasis occurs in up to 15% of patients, usually children. Arthritis and psoriasis may present simultaneously.
  • Psoriasis occurs in 2–3% of the U.S. population; 6–42% will develop PsA (1).

Prevalence
Prevalence: 1 to 2/1,000 population (1)

Etiology and Pathophysiology

  • CD4+/CD8+ T cells; tumor necrosis factor α (TNF-α); interleukin 1 (IL-1), IL-6, IL-8, IL-10, IL-17 and IL-23; and matrix metalloproteases present in synovial fluid
  • Osteoclast precursor cell upregulation
  • Unknown. Probably multifactorial: immunologic, genetic, environmental factors

Genetics

  • 30–40% concordance in identical twins
  • HLA-B27 in 15–50% with PsA (spondylitis pattern) versus 90% in AS
  • Other HLA associations in PsA: HLA-B7, HLA-B38, HLA-B39, HLA-Cw6

Risk Factors

  • Psoriasis
  • Family history of PsA
  • Obesity

General Prevention

No known prevention strategies; unknown whether early treatment of psoriasis prevents onset of PsA

Commonly Associated Conditions

Psoriasis

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