Ankylosing Spondylitis

• Ankylosing spondylitis is a chronic, multi-system inflammatory disorder characterised inflammation of the sacroiliac joints and axial skeleton.
• seronegative Spondyloarthropathies:

  • Ankylosing spondylitis
  • Psoriatic arthritis
  • Reactive arthritis
  • IBD-associated spondyloarthropathy
  • the ‘seronegative’ label refers to both the lack of rheumatoid factor positivity and the absence of specific antibodies for each disease.
• The typical presentation is a young adult male in their 20s. Symptoms develop gradually over at least three months.

  The main presenting features are

  • Pain and stiffness in the lower back
  • Sacroiliac pain (in the buttock region)
• Chronic lower back pain and morning stiffness are characteristic of AS. Starts insidiously at a young age (<45)
• Clinical features:

  • Back pain - worse with inactivity, improves with exercise
  • Neck pain
  • Alternating buttock pain
  • Morning stiffness
  • Fatigue
  • Arthritis
  • Enthesitis (inflammation at the insertion of tendons and ligaments)
  • Positive schober test (assess decrease in lumbar spine flexion)
  • Spinal deformity
  • Extra-articular manifestation s
• Schober test:

  • L5 spinous process is identified and marked with patient standing up (typically lies at the level of the sacral dimples)
  • Another line made 10cm above first line
  • Patient asked to bend forward and touch toes
  • Distance between 2 lines is remeasured
  • Increase of <5cm during flexion is considered a positive test
• Spinal deformity:

  • Hunched back is common due to hyperkyphosis of the thoracic vertebrae
  • In more advanced disease - question mark posture:
  • Thoracic hyperkyphosis
  • Loss of lumbar lordosis
  • Flexion deformities of hips and neck
• Additional symptoms and problems include:

  • Chest pain - related to the costovertebral and sternocostal joints
  • Enthesitis - inflammation of the entheses, where tendons or ligaments inset into bone
  • Dactylitis - inflammation of the entire finger
  • Vertebral fractures - sudden onset new neck or back pain
  • Shortness of breath - restricted chest wall movement
• Associations (the 5 As):

  • Anterior uveitis
  • Aortic regurgitation
  • Atrioventricular block
  • Apical lung fibrosis
  • Anaemia of chronic disease
• Key investigations include:

  • Inflammatory markers (e.g., CRP and ESR) may rise with disease activity
  • HLA B27 genetic testing (negative test does not exclude the diagnosis)
  • X-ray of the spine and sacrum - sacroiliitis
  • MRI of the spine can show bone marrow oedema early in the disease before there are any xray changes
• A “bamboo spine” is the typical x-ray finding in the later stages of ankylosing spondylitis, where there is fusion of the sacroiliac and spinal joints.
• X-rays in ankylosing spondylitis can show:

  • Squaring of the vertebral bodies
  • Subchondral sclerosis and erosions
  • Syndesmophytes (areas of bone growth where the ligaments insert into the bone)
  • Ossification of the ligaments, discs and joints (these structures start turning into bone)
  • Fusion of the facet, sacroiliac and costovertebral joints
• One of the most commonly used criteria to aid the diagnosis of AS is the 1984 Modified New York Criteria
• Medical management may involve:

  • Non-steroidal anti-inflammatory drugs (NSAIDs) are first-line
  • Anti-TNF medications are second-line (e.g., adalimumab, etanercept or infliximab)
  • Secukinumab or ixekizumab are third-line (monoclonal antibodies against interleukin-17)
  • Upadacitinib is another third-line option (JAK inhibitor)
• Intra-articular steroid injections may be considered for specific joints.
• Additional management:

  • Physiotherapy
  • Exercise and mobilisation
  • Avoiding smoking
  • Bisphosphonates for osteoporosis
  • Surgery is occasionally required for severe joint deformity
• Complications:

  • Spinal fusion - limits mobility
  • Spinal fractures - higher risk as the disease progresses
  • Osteoporosis
  • Restrictive lung disease
  • Spinal cord injury - due to fractures or stenosis
  • Cardiac disease - valvular disease, heart failure and arrhythmias