Psoriatic arthropathy

Psoriatic arthropathy is an inflammatory arthritis associated with psoriasis and is classed as one of the seronegative spondyloarthropathies. It correlates poorly with cutaneous psoriasis and often precedes the development of skin lesions. Around 10-20% of patients with skin lesions develop an arthropathy, with males and females being equally affected.

Presentation

Patterns

• symmetric polyarthritis
  • very similar to rheumatoid arthritis
  • 30-40% of cases, most common type
• asymmetrical oligoarthritis: typically affects hands and feet (20-30%)
  • historically thought to be the most common type, based on older data (e.g. 1973 Moll and Wright), though more recent studies suggest symmetric polyarthritis may now be more prevalent
• sacroiliitis
• DIP joint disease (around 10%)
• arthritis mutilans: a severe deforming form with 'telescoping fingers'

Other signs

• psoriatic skin lesions
• periarticular disease - tenosynovitis and soft tissue inflammation resulting in:
  • enthesitis: inflammation at the site of tendon and ligament insertion (e.g. Achilles tendonitis, plantar fasciitis)
  • tenosynovitis: typically of the flexor tendons of the hands
  • dactylitis: diffuse swelling of an entire finger or toe
• nail changes
  • pitting
  • onycholysis

Investigation and Management

Bloods

• CRP/ESR typically elevated due to inflammation
• as a seronegative spondyloarthropathy, rheumatoid factor (RF) and anti-cyclic citrullinated peptide antibodies (anti-CCP) are usually negative
• HLA-B27 may be positive, particularly in patients with axial involvement

X-ray

• may show a combination of erosions and new bone formation