Ankylosing spondylitis

Key features:

- Ankylosing spondylitis encompasses a group of rheumatic disorders that share clinical, genetic and radiographic features and includes psoriatic arthritis, reactive arthritis or inflammatory bowel disease.

- Affects 1 in 200 individuals and is usually diagnosed many years after onset of symptoms . Chronic back pain is common and recognition of early disease requires clinical experience and a high index of suspicion. Further, inflammatory markers are not invariably elevated and radiographic changes are often late findings.

  - The presence of inflammatory back pain (IBP), the archetypal feature of AS, increases the likelihood of SpA to approximately 14%.

- Two very specific features of IBP are alternating buttock pain and awakening only in the second half of the night with spinal pain or stiffness. Table listed the difference between inflammatory and mechanical back pain

- Examination findings:

• Reduced spinal mobility: modified schober's test, lumbar side flexion and occiput to wall distance.
• Extra axial features: 50% asymmetric oligoarthrits (< 4joints), often targeting the lower limb joins, enthesitis and dactylitis.
• Extra-articular features: uniocular anterior uveitis in 40% of patients (presents with acute painful red eye, blurred vision and photophobia)

- Investigation findings: 

• Lab test: CRP, ESR (Only 50-70% of AS patients), HLA-B27
• Imaging: x-rays

References:

- http://www.racgp.org.au/download/Documents/AFP/2013/November/201311golder.pdf