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Psoriatic arthritis

Psoriatic arthritis is a polygenic disorder. HLA-Cw6 is associated with severe, early-onset skin psoriasis. HLA-B38 and HLA-B39 are associated with psoriatic arthritis and HLA-B27 is associated with sacroiliitis and spondylitis. Notably, only 50% of patients with psoriatic sacroiliitis/spondylitis are HLA-B27 positive.

Clinical features that suggest psoriatic arthritis

• Asymmetric joint involvement.

• Absence of rheumatoid factor.

• Significant nail pits (>60 total pits is pathognomonic) or nail dystrophy.

• Involvement of DIP joints in the absence of osteoarthritis.

• “Sausage digits” (dactylitis): seen in 30% to 50%. Due to synovitis and flexor tenosynovitis.

• Enthesitis: seen in 35% to 40%. Most common Achilles and plantar fascia insertion.

• Family history of psoriasis or psoriatic arthritis.

• Axial radiographic evidence of sacroiliitis, paravertebral ossification, and syndesmophytes.

• Peripheral radiographic evidence of erosive arthritis with relative lack of periarticular osteopenia.

• Synovial biopsies show increased vascularity and the presence of macrophages(CD163+), lymphocytes, and neutrophils.

Classification of Psoriatic Arthritis criteria (CASPAR)

  1. Evidence of psoriasis (current, past, family): two points if current history of psoriasis, one point others.
  2. Psoriatic nail dystrophy: one point
  3. Negative rheumatoid factor: one point.
  4. Dactylitis (current, past history): one point.
  5. Radiographic evidence of juxtaarticular new bone formation: one point.

Three or more points have 99% specificity and 92% sensitivity for diagnosis of psoriatic arthritis.

Classification of Joint Involvement in Psoriatic Arthritis

SUBTYPE

PERCENTAGE

TYPICAL JOINTS

Asymmetric oligoarticular disease

15 to 20

DIP joints and PIP joints of hands and feet. MCP joints, MTP joints, knees, hips, and ankles

Predominant DIP involvement

2 to 5

DIP joints

Arthritis mutilans

5

DIP joints, PIP joints

Polyarthritis “rheumatoid-like”

50 to 60

MCP joints, PIP joints, and wrists

Axial involvement (isolated)

2 to 5

Sacroiliac, vertebral

DIP, Distal interphalangeal; MCP, metacarpophalangeal; MTP, metatarsophalangeal; PIP, proximal interphalangeal.


Patients should be treated similar to other inflammatory arthritides. Polyarticular disease and an elevated ESR/CRP indicate a worse prognosis. Some patients can be managed with nonsteroidal antiinflammatory drugs (NSAIDs) alone. Intraarticular steroid injections are also helpful in joints that are resistant to NSAIDs and proven not to be infected. Methotrexate, sulfasalazine, leflunomide, and cyclosporine have all been reported to have a small effect on skin involvement, peripheral arthritis, enthesitis, and dactylitis. However, none of these medications have been shown to halt radiographic progression and none are effective for axial disease or nail disease. Owing to large amounts of TNF-α found in psoriatic arthritis synovium, anti-TNF-α agents with or without methotrexate have been shown to be effective therapy for arthritis, dactylitis, enthesitis, spondylitis, and skin disease. Obesity appears to lessen the effectiveness of anti-TNF agents.



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Hopkins Arthritis

National Psoriasis Foundation

Healthline

MayoClinic

NHS UK

Patientenbroschüre Rheumaliga Schweiz (German)