Ankylosing spondylitis

Definition

An axial seronegative spondyloarthritis characterized by sacroiliitis and progressive spinal disease

≥3 months of back pain, and
Onset ≤45 years, and
Either of:
- Sacroiliitis on imaging and 1 or more features of spondyloarthritis
- HLA-B27 positive and 2 or more features of spondyloarthritis
Where
- Sacroiliitis on imaging means either:
  - Definite evidence based on modeified NY criteria
  - Active inflammation on MRI
- Spondyloarthritis features are:
  - Inflammatory back pain
  - Response to NSAIDs
  - Family history of spondyloarthritis
  - HLA-B27 positive
  - Elevated CRP
  - Extra-spinal manifestations
    - Arthritis
    - Enthesitis
    - Uveitis
    - Dactylitis
    - Inflammatory bowel disease
    - Psoriasis

Ache and tenderness of lumbar or gluteal regions
Hip arthritis in 30%, shoulder arthritis in less
Bony tenderness of costosternal junctions, spinous processes, iliac crests, greater trochan- ters, ischial tuberosities, tibial tubercles, and heels
Peripheral arthritis in 30% of patients, usually asymmetric
Sequelae
- Acute anterior uveitis in 40%
  - Unilateral painful, teary eye with photophobia
- Aortic insufficiency (early)
- Third-degree heart block
- Cauda equina syndrome and upper pulmonary lobe fibrosis (rare, late)
- Retroperitoneal fibrosis (rare)

Modified Schober test
- Marks made on the spine at lumbosacral junction (line between the PSISs) and 10 cm above
- Maximal forward flexion with knees straight
- Normal ≥5cm, restricted <4cm

Labs
- HLA-B27 helpful but neither sufficient nor necessary
  - 90% of ank spon patients have HLA-B27
- CRP, elevated
Imaging
- X-ray of the SI joints
- If x-ray negative but suspicion high, consider MRI

All patients should participate in active, land-based physical therapy
First-line: NSAIDs for a two-week trial
- Naproxen 500mg PO BID
- Meloxicam 7.5mg PO BID
Second-line, if fails two NSAIDs: biologics
- Specifically, TNF-alpha inhibitors
- Etanercept
DMARDs NOT helpful (i.e. methotrexate, sulfasalazine)