Description

• PsA is a seronegative spondyloarthropathy characterized by inflammatory arthritis and enthesitis.
• 5 patterns of arthritis in PsA:
  • Asymmetric oligoarthritis: Involves <5 small or large joints
  • Distal interphalangeal (DIP) joint predominant: Osteoarthritislike, often associated with nail psoriasis
  • Symmetric polyarthritis: May be indistinguishable from rheumatoid arthritis (RA), but typically milder clinical course
  • Spondyloarthritis: Asymmetric and discontinuous, unlike ankylosing spondylitis (AS)
  • Arthritis mutilans: Destructive, resorptive arthritis; produces so-called opera-glass or telescoping digit
• Although psoriasis generally is present, it may be limited in extent:
  • Course of arthritis and extent of psoriasis do not appear to correlate.
  • Other extra-articular features, such as iritis, are less common.
  • Damaging joint disease may occur in 40–57%. Characteristic radiologic changes include joint erosions that begin marginally and move centrally (“pencil-in-cup deformity”) and periostitis.
• Rheumatoid factor (RF) and cyclic citrullinated peptide (anti-CCP) antibody are usually negative. HLA-B27 may be positive.

Epidemiology

• Peak onset age: 30–50 years
• Predominant gender: Female = Male
• Polyarthritis is more common in women.
• Spondylitis in up to 25%, more common in males
• Psoriasis precedes arthritis in the majority by an average of 12 years. Arthritis may precede psoriasis in up to 15%, and this occurs more often in children. Arthritis and psoriasis also may present simultaneously.
• Psoriasis occurs in 2–3% of the US population; 6–42% of these individuals develop PsA (1).

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

Risk Factors

• Psoriasis
• Family history of PsA

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

General Prevention

There are no currently available prevention strategies. It is unknown if early systemic treatment of psoriasis prevents the onset of PsA.

Pathophysiology

• CD4+/CD8+ T cells; tumor necrosis factor α (TNF-α); interleukins 1 (IL-1), 6, 8, and 10; and matrix metalloproteases present in synovial fluid (2)
• Osteoclast precursor cell upregulation

Etiology

Unknown. Probably multifactorial: Immunologic, genetic, environmental factors

Commonly Associated Conditions

Psoriasis