MRCP PACES Rheumatology Ankylosing Spondylitis
Ankylosing spondylitis. Credit: Mehlauge, CC BY-SA 3.0, via Wikimedia Commons

Clinical features

  • Males more commonly affected (2.5 : 1)
  • Inflammatory back pain
    • Typically starts in third or fourth decade of life
    • Insidious onset
    • Worse in the morning or after periods of immobility
    • Better with exercise
    • May have difficulty sleeping
    • Not relieved by resting
    • May have buttock pain (sacroiliac involvement)
    • Can have symptoms anywhere along the spine
    • Relieved by NSAIDs
    • Family history of spondyloarthropathy
  • Other manifestations
    • Peripheral arthritis
    • Enthesitis
    • Dactylitis
    • Anterior uveitis (acute, unilateral painful red eye with photophobia, blurring of vision)
    • Aortic regurgitation (sclerosing inflammation resulting in decreased elasticity of the aortic root)
    • Extra-Athoracic restrictive lung disease (diminished chest wall and spinal mobility)
    • Apical pulmonary fibrosis
  • Spinal involvement
    • Modified Schober test (anterior lumbar spinal flexion)
      • Midpoint of the line joining the two posterior superior iliac spines
      • Note the position 10cm above and 5cm below this point with the patient standing
      • Ask the patient to bend forward as much as possible, while keeping legs straight
      • Distance between the two points should increase by ≥ 5cm
    • Lateral cervical and lumbar spinal flexion
    • Occiput to wall distance (normal people should be able to touch occiput to wall when standing)
    • Cervical spine and thoracic spine rotation
  • Complications
    • Spinal cord injury secondary to pathological fractures
    • Atlanto-axial subluxation
    • Cauda equina syndrome
  • Commonly co-exists with
    • Psoriasis
    • Inflammatory bowel disease

Investigations

Bamboo spine. Stevenfruitsmaak, CC BY-SA 3.0, via Wikimedia Commons
  • Full blood count (anaemia of chronic disease)
  • Renal function, liver function (prior to starting NSAIDs or definitive therapy)
  • HLA-B27 (positive in 90% of patients with AS, but not specific)
  • Plan radiograph of the pelvis and spine
    • Scaroilitis
    • Erosions, osteitis at bony prominences
    • Presence of syndesmophytes (bony growths within ligaments) – bamboo spine
  • Magnetic resonance imaging of sacroiliac joints to look for active inflammation
  • Trans-thoracic echocardiogram to assess aortic valve if history and examination suggestive
  • High-resolution computed tomography scan of the lungs to look for apical fibrosis
  • Pulmonary function testing to look for restrictive lung disease

 Management

  • NSAIDs (first-line treatment): continuous use can slow radiographic progression
  • Conventional DMARDs have no role in the treatment of AS (they are not effective)
  • TNF-α inhibitors
    • Indicated in patients who have inadequate response to at least two NSAIDS used for ≥4 weeks each
    • Choices: etanercept, adaliumumab, golimumab, infliximab
    • > 60% response rate
    • May switch to a different TNF-α inhibitor if response to the first decreases
    • Reduces radiographic progression of AS
  • Rituximab (anti-CD20)
    • May have some efficacy in TNF-α naïve patients
    • Currently role in AS is unclear
  • Newer targets
    • Anti-IL12/23: ustekinumab
    • Anti-IL17: secukinumab
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