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Ankylosing Spondylitis N005

Last amended 
8 April 2021
Current RMA Instruments
Reasonable Hypothesis SOP
39 of 2021
Balance of Probabilities SOP
40 of 2021
Changes from previous Instruments

SOP Bulletin 220

 ICD Coding
  • ICD-9-CM Codes: 720.0
  • ICD-10-AM Codes: M45
Brief description

This is an uncommon, chronic, progressive, systemic, inflammatory condition which mainly affects the spine (spondylitis) and sacroiliac joints and causes chronic back pain.  There can also be manifestations outside the spine, see note below.

Confirming the diagnosis  

The diagnosis is based on a combination of clinical findings, laboratory results and imaging.  The diagnosis is often difficult to establish and specialist opinion will be needed.  Testing will typically include HLA-B27 (a genetic marker) testing and plain X-rays or MRI of involved joints.  There is no one single finding that will confirm the diagnosis. 

The appropriate medical specialist is a rheumatologist.

Additional diagnoses covered by SOP
  • Axial spondyloarthritis
  • Marie-Strumpell disease
  • Von Bechterew’s disease
Additional diagnoses which may be covered (further information required)
  • HLA B27 spondyloarthropathy
  • Inflammatory sacroilitis
  • Sero-negative spondyloarthropathy
Conditions excluded from SOP
  • Osteoarthritis or spondylosis* of spine
  • Spondyloarthropathy – due to reactive arthritis*, psoriatic arthritis* or inflammatory bowel disease*
  • Rheumatoid arthritis of the spine*

* another SOP applies

Clinical onset

Onset is typically insidious and before the age of 45 (peak is between 20 and 30 years).  The most common presentation is with chronic dull pain in the lower back or buttock.

Clinical worsening

The only SOP worsening factor is for inability to obtain appropriate clinical management.  There is no curative treatment but there are medications that can slow or stop the progress of the disease.  The clinical course is variable.

Note: Other manifestations of ankylosing spondylitis

This systemic disease may have other manifestations:

  • Inflammation in other joints:
    • hip and shoulder
    • peripheral joints
    • costovertebral, chostochondral, sternoclavicular joints
  • Enthesitis - inflammation of some tendon-bone insertions
  • Dactylitis - inflammation and swelling of fingers
  • Eye changes – anterior uveitis
  • Cardiac problems – aortic regurgitation; conduction abnormalities
  • Pulmonary changes – apical pulmonary fibrosis

There may also be complications arising from the spinal pathology such as: spinal stenosis with radiculopathy and myelopathy; localised osteoporosis; and spinal compression fractures.