Ankylosing spondylitis

Definition

• An axial seronegative spondyloarthritis characterized by sacroiliitis and progressive spinal disease

Risk Factors

• Age 20s to 30s
• Male to female ratio of 2:1 to 3:1

Diagnostic Criteria (ASAS)

• ≥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

Clinical Manifestations

• 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)

Physical exam

• 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

BASDAI

• Disease activity measure

Investigations

• 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

Management

• 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)