Axial Spondyloarthritis

 

• Pathophysiology and epidemiology

  • Spondyloarthritis (SpA) is a group of autoimmune conditions involving arthritis (primarily enthesitis, where tendon meets bone) and extra-articular manifestations. SpA can be axial – primarily affecting the spine – or peripheral, though both may have features of the other.
  • Axial SpA is known as ankylosing spondylitis when it is radiographically confirmed, and non-radiographic axial SpA otherwise. Historically (and still to many clinicians), all axial SpA was known as ankylosing spondylitis.
  • Onset usually under 35 years, and while traditionally thought to be much commoner in men, there may in fact be only minimal gender differences.

• Presentation

  Key features:

  • Insidious onset of symptoms over several years.
  • Morning stiffness and pain in the lower back lasting for hours. May wake them.
  • Buttock pain and sacroiliac joint tenderness.
  • Reduced spinal movement leads to reduced thoracic expansion.
  • Peripheral joint involvement (30%), usually asymmetric and lower limb.
  • Enthesitis: dactylitis, plantar fasciitis, achilles tendonitis, and costochondritis.

  Later features:

  • Question mark posture: kyphosis and neck extension.
  • Osteoporosis and osteoarthritis.

  Extra-articular manifestations and co-morbidities, the 5As:

  • Anterior uveitis (25%), especially iritis.
  • Autoimmune bowel disease (7%): Crohn's or ulcerative colitis (note if joint symptoms are primarily peripheral, known as enteropathic SpA).
  • Apical lung fibrosis.
  • Aortic regurgitation.
  • Amyloidosis

  Psoriasis may also be present, though if joint symptoms are primarily peripheral, it is likely to be psoriatic arthritis.

• Investigations and diagnosis

  Imaging:

  • X-ray: sacroiliitis – including sclerosis and erosions – and enthesitis. Often normal in early disease. Later shows ankylosis, fusion of vertebrae to create a 'bamboo spine'.
  • MRI is more sensitive in the early stages.
  • DEXA to screen for osteoporosis.

  Bloods:

  • Normocytic anaemia.
  • ↑ESR/CRP
  • ↑Alk phos.
  • HLA-B27: 90% sensitive and specific.

  Diagnose with the Assessment of SpA international Society (ASAS) criteria, which requires a compatible clinical history plus radiographic sacroiliitis or HLA-B27.

• Management

  Lifestyle:

  • Exercise and physio to maintain posture and movement.

  Medical:

  • NSAIDs: ibuprofen, diclofenac, naproxen, or celecoxib. Use at lowest-effective dose and give PPI too.
  • Steroid injections can provide short-term relief e.g. sacro-iliac, tendons.
  • Anti-TNF alpha monoclonal antibodies if there is {high disease activity} plus {CRP or radiographic evidence of inflammation} plus {2 NSAIDs have failed}. Switch to secukinumab (anti IL-17A) if anti-TNF alpha ineffective.
  • Bisphosphonates if osteoporosis develops.

  Surgical:

  • Vertebral osteotomy to correct deformities.
  • Arthroplasty if hip affected.