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 is part of the seronegative spondyloarthropathies (negative for RF/anti-CCP). Presentation ranges from mild oligoarthritis to severe, deforming arthritis (arthritis mutilans). ⚠️ Severe PsA is more common in HIV-positive patients. Early recognition and prompt treatment prevent irreversible joint damage and disability.

📊 Overview

• Seronegative arthritis (RF/anti-CCP negative).
• Psoriasis usually precedes arthritis but PsA can rarely precede skin lesions.
• Affects both peripheral joints and axial skeleton (sacroiliac joints, spine).
• Equal sex distribution; peak age 30–55 yrs.

🧬 Aetiology & Pathophysiology

• Genetic: HLA-B27 (axial disease), HLA-Cw6 (skin involvement).
• Immune-mediated: T-cell and cytokine-driven (TNF-α, IL-17, IL-23).
• Triggers: Trauma (Koebner phenomenon), infection, environmental factors.
• Pathophysiology: Enthesitis → synovitis → bone erosion and proliferation → characteristic deformities.

🔎 Key Radiological Feature

🖊️ Pencil-in-Cup Deformity: distal bone tapering into adjacent bone cup, classic 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 involvement.
  • Dactylitis = “sausage digit”.
  • Arthritis mutilans → destructive, deforming joints.
  • Axial disease → sacroiliitis, spinal stiffness, enthesitis.
• Extra-articular 🌍: Anterior uveitis, conjunctivitis, pulmonary fibrosis, aortic regurgitation.

📌 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 Classification 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 on X-ray = +1

🧪 Investigations

• Bloods: FBC (may show anaemia of chronic disease), ESR/CRP ↑, RF/anti-CCP negative.
• Imaging:
  • X-ray: erosions, joint narrowing, periostitis, bony proliferation, pencil-in-cup deformity.
  • MRI: early axial disease, sacroiliitis, enthesitis.
  • Ultrasound: synovitis, tenosynovitis, and enthesitis detection.

💊 Management (NICE-aligned, Treat-to-Target)

• Principle: Early intervention prevents joint destruction. Tailor therapy to dominant phenotype (peripheral, axial, enthesitis, dactylitis, skin).
• 🟢 Lifestyle & Supportive:
  • Patient education, shared decision-making.
  • Weight management (obesity reduces biologic efficacy).
  • Smoking cessation.
  • Physiotherapy and occupational therapy for joint function.
• 🟡 Symptomatic Relief:
  • NSAIDs for pain/stiffness (monitor CV/GI risk).
  • Intra-articular steroid injections for isolated joints.
  • Systemic steroids cautiously (risk of psoriasis rebound).
• 🟠 Conventional DMARDs (peripheral arthritis):
  • Methotrexate – first-line for peripheral arthritis and skin disease.
  • Sulfasalazine or Leflunomide – alternatives.
  • Limited efficacy for axial disease.
• 🔵 Biologic / Targeted Therapy (moderate–severe or DMARD-refractory):
  • Anti-TNF agents (etanercept, adalimumab, infliximab)
  • IL-17 inhibitors (secukinumab, ixekizumab)
  • IL-23 inhibitors (guselkumab)
  • JAK inhibitors (upadacitinib) in selected patients
• 🔴 Axial PsA:
  • NSAIDs first-line.
  • Persistent disease → biologics (anti-TNF or IL-17 inhibitors).
  • Conventional DMARDs usually ineffective.
• Monitoring & Screening:
  • Regular assessment of joint and skin disease activity.
  • Screen for uveitis, inflammatory bowel disease, cardiovascular risk, metabolic syndrome.
  • Adjust therapy per treat-to-target principles (low disease activity or remission).
• Surgical: Synovectomy or joint replacement in advanced destructive disease.

💡 Student Tips

• Remember: PsA = seronegative, often with nail changes and dactylitis.
• Pencil-in-cup deformity is classic for exam radiology questions.
• Assess for axial involvement separately – different management pathway.
• Always consider comorbidities: CV risk, metabolic syndrome, IBD, HIV.

📚 References

• NICE CKS – Psoriatic Arthritis
• Psoriatic Arthritis: A Review
• EULAR 2023 Recommendations: EULAR Management of PsA