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Spondyloarthropathies

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SpA Overview - Backbone Blues Brigade

  • Group of inflammatory rheumatic diseases, seronegative for Rheumatoid Factor.
  • Strong genetic link: HLA-B27 positive in many.
  • Hallmarks:
    • Axial skeleton: Sacroiliitis (SI joint inflammation), Spondylitis (vertebral inflammation).
    • Peripheral arthritis: Often asymmetric, oligoarticular, predominantly lower limb.
    • Enthesitis: Inflammation at sites of tendon/ligament attachment to bone (e.g., heel pain).
    • Dactylitis: Diffuse swelling of a finger/toe ("sausage digit").
  • Common extra-articular features: Anterior uveitis, psoriasis, inflammatory bowel disease. Spondyloarthritis: Affected Body Areas and Other Symptoms

⭐ Asymmetric oligoarthritis, particularly of the lower limbs, is characteristic of peripheral involvement in SpA.

Ankylosing Spondylitis - Bamboo Spine Saga

  • Chronic inflammation of sacroiliac (SI) joints & axial skeleton. HLA-B27 positive (~90%). Predominantly affects males < 45 yrs.
  • Key Features:
    • Axial: Inflammatory back pain (>3 months, nocturnal, improves with exercise, not with rest), morning stiffness.
    • Peripheral: Asymmetric oligoarthritis (mainly lower limb), enthesitis (e.g., Achilles tendonitis, plantar fasciitis).
    • Extra-articular: Acute anterior uveitis (most common), Aortitis, Apical pulmonary fibrosis. 📌 (AAA)
  • Diagnosis:
    • Clinical findings + Radiographic evidence of sacroiliitis (X-ray/MRI).
    • Modified New York (mNY) criteria often used for classification.
    • Classic "Bamboo Spine" appearance on X-ray (late finding due to syndesmophytes & vertebral fusion). Ankylosing Spondylitis: Bamboo Spine X-ray
  • Management: Physiotherapy/exercise, NSAIDs (first-line). Biologics (TNF-α inhibitors, IL-17 inhibitors) for refractory axial disease.

⭐ Schober's test (normal: >5 cm increase from 10 cm mark on lumbar flexion) is used to assess lumbar spine mobility; reduced in AS.

Psoriatic Arthritis - Scaly Joint Story

Seronegative inflammatory arthritis associated with psoriasis. Often HLA-B27 positive, especially with axial disease.

  • Patterns of Articular Involvement:
    PatternDescription
    Asymmetric OligoarthritisMost common; oligoarticular (<5 joints)
    Symmetric PolyarthritisRA-like; polyarticular (small/large jts)
    DIP PredominantDIP joint involvement
    Arthritis MutilansSevere, deforming; "opera-glass hand"
    SpondyloarthritisAxial involvement, sacroiliitis
  • Key Features:
    • Dactylitis ("sausage digits")
    • Enthesitis (e.g., Achilles tendinitis)
    • Nail changes (pitting, onycholysis)
  • Radiology: "Pencil-in-cup" deformity.
  • Diagnosis: CASPAR criteria (≥3 points). Psoriatic arthritis: dactylitis and nail changes

⭐ Dactylitis and DIP joint involvement are highly characteristic of Psoriatic Arthritis.

Reactive & Enteropathic Arthritis - Gut Reaction Joints

  • Reactive Arthritis (ReA):
    • Trigger: Post-GI (Shigella, Salmonella, Yersinia, Campylobacter) or GU (Chlamydia) infection (1-4 weeks).
    • 📌 Triad: "Can't see (conjunctivitis), can't pee (urethritis), can't climb a tree (arthritis)".
    • Features: Asymmetric oligoarthritis (lower limbs), dactylitis, enthesitis.
    • HLA-B27 positive in 50-80%.
  • Enteropathic Arthritis (EnA):
    • Linked to IBD (Crohn's Disease, Ulcerative Colitis).
    • Peripheral type: Large joint arthritis, activity mirrors gut inflammation.
    • Axial type: Sacroiliitis/spondylitis, independent of gut flares, strong HLA-B27 link.
    • ⭐ > Peripheral arthritis in EnA typically flares with IBD activity, whereas axial disease often follows an independent course.

SpA Diagnosis & Management - Unraveling & Repairing

  • Diagnosis: ASAS criteria are key.
    • Imaging arm: Sacroiliitis (X-ray/MRI) + ≥1 SpA feature.
    • Clinical arm: HLA-B27 positive + ≥2 other SpA features.
  • Management Strategy:
    • 1st line: NSAIDs, consistent physiotherapy.
    • Peripheral arthritis: csDMARDs (Sulfasalazine, Methotrexate).
    • Axial disease/refractory cases: bDMARDs (TNF-α inhibitors, IL-17 inhibitors) or tsDMARDs (JAK inhibitors).
    • Local glucocorticoid injections for monoarthritis/enthesitis.

⭐ TNF-α inhibitors are contraindicated in patients with demyelinating diseases (e.g., MS) or NYHA Class III/IV heart failure.

High‑Yield Points - ⚡ Biggest Takeaways

  • Spondyloarthropathies: group of inflammatory arthritides, strongly linked to HLA-B27.
  • Key features: axial skeletal involvement (sacroiliitis, spondylitis), enthesitis, dactylitis.
  • Typically seronegative for Rheumatoid Factor (RF) and often ANA.
  • Ankylosing Spondylitis: progressive spinal fusion ("bamboo spine"), morning stiffness.
  • Reactive Arthritis: classic triad of arthritis, urethritis, and conjunctivitis/uveitis. (Mnemonic: "can't see, pee, or climb a tree").
  • Psoriatic Arthritis: associated with psoriasis; "pencil-in-cup" deformity, nail changes.
  • Common extra-articular links: anterior uveitis, IBD, and psoriatic lesions.

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