Spondyloarthropathies

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.

⭐ 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).
• 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:

  Pattern	Description
  Asymmetric Oligoarthritis	Most common; oligoarticular (<5 joints)
  Symmetric Polyarthritis	RA-like; polyarticular (small/large jts)
  DIP Predominant	DIP joint involvement
  Arthritis Mutilans	Severe, deforming; "opera-glass hand"
  Spondyloarthritis	Axial 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).

⭐ 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.