Psoriatic arthritis

Related Subjects: |Monoarticular arthritis |Polyarticular arthritis |Seronegative Spondyloarthropathies |Ankylosing spondylitis |Enteropathic Spondyloarthritis |Reactive Arthritis

🦴 Psoriatic Arthritis (PsA) is a chronic inflammatory arthritis associated with psoriasis. It belongs to the seronegative spondyloarthropathies (negative for RF/anti-CCP). Presentation ranges from mild oligoarthritis to severe, deforming arthritis. ⚠️ Severe PsA is more common in HIV-positive patients.

📊 About

• PsA is a seronegative arthritis (RF/anti-CCP negative).
• Psoriasis usually precedes arthritis, but PsA can occur before skin lesions.
• Affects both axial and peripheral skeleton.

🧬 Aetiology

• Affects men and women equally; peak age 30–55 yrs.
• Genetic: HLA-B27, HLA-Cw6 association.
• Immune-mediated: T-cell and cytokine (TNF-α, IL-17, IL-23) driven.
• Triggers: Trauma (Koebner phenomenon), infections, environmental exposures.

🔎 Key Radiological Finding

🖊️ Pencil-in-Cup Deformity: end-bone erosion with tapering into adjacent bone cup, typical of advanced PsA.

🩺 Clinical Features

• Skin 🖐️: Psoriasis on scalp, elbows, knees, umbilicus, natal cleft, palms/soles.
• Nails 💅: Pitting, onycholysis, “oil drop” sign.
• Joints:
  • Asymmetrical oligoarthritis (most common).
  • Symmetrical polyarthritis (RA-like).
  • DIP arthritis → often with nail changes.
  • Dactylitis = “sausage digit”.
  • Arthritis mutilans → destructive, deforming.
  • Axial disease with sacroiliitis, spinal stiffness.
• Extra-articular 🌍: Pulmonary fibrosis, aortic regurgitation, anterior uveitis/conjunctivitis.

📌 Patterns of Joint Involvement

• 👆 DIP predominant (linked to nail disease).
• ✋ Asymmetrical oligoarthritis (knees, large joints).
• 🤲 Symmetrical polyarthritis (mimics RA).
• 🦴 Arthritis mutilans (rare, severe).
• 🧍 Axial arthritis (sacroiliitis, spine).

🧾 CASPAR Criteria (≥3 points)

• Psoriasis (current = +2; past/family = +1).
• Nail dystrophy (pitting/onycholysis) = +1.
• Dactylitis (past or present) = +1.
• RF negative = +1.
• Juxta-articular new bone formation (X-ray) = +1.

🧪 Investigations

• Bloods: FBC (anaemia), ↑ESR/CRP, RF/anti-CCP negative.
• Imaging:
  • X-ray: erosions, joint narrowing, bony proliferation, periostitis, pencil-in-cup deformity.
  • MRI: useful for sacroiliitis and early axial disease.

💊 Management of Psoriatic Arthritis (PsA)

• Principle: Early treatment using a treat-to-target approach to prevent joint damage and disability. Assess pattern first: peripheral, axial, enthesitis, dactylitis, skin-dominant.
• 🟢 Conservative & Lifestyle:
  • Patient education and shared decision-making.
  • Weight reduction (obesity reduces biologic response).
  • Smoking cessation.
  • Physiotherapy and exercise (maintain mobility and function).
• 🟡 Symptomatic Relief:
  • NSAIDs for pain and stiffness (short term; monitor GI/CV risk).
  • Intra-articular steroid injections for isolated joint inflammation.
  • Systemic steroids used cautiously (risk of psoriasis rebound on withdrawal).
• 🟠 Conventional DMARDs (peripheral disease):
  • Methotrexate (first-line for peripheral arthritis and skin involvement).
  • Sulfasalazine or Leflunomide as alternatives.
  • Note: Conventional DMARDs have limited effect in axial disease.
• 🔵 Biologic / Targeted Therapy (moderate–severe or inadequate response):
  • Anti-TNF agents (e.g., etanercept, adalimumab, infliximab).
  • IL-17 inhibitors (e.g., secukinumab, ixekizumab).
  • IL-23 inhibitors (e.g., guselkumab).
  • JAK inhibitors (e.g., upadacitinib) in selected patients.
• 🔴 Axial PsA:
  • NSAIDs first-line.
  • If persistent → biologic therapy (anti-TNF or IL-17 inhibitor).
  • Conventional DMARDs are generally ineffective for axial symptoms.
• 🧠 Monitor & Screen:
  • Assess disease activity regularly (joints + skin).
  • Screen for uveitis, IBD, metabolic syndrome, and cardiovascular risk.

📚 References

• Psoriatic Arthritis: A Review
• NICE CKS – Psoriatic Arthritis