Axial Spondyloarthritis

Basics

Description

  • Chronic inflammatory arthritis of the spine with predilection toward the spine and sacroiliac (SI) joints
  • Encompasses Axial Spondylitis (AKA anklyosing spondylitis) and nonradiographic axial spondyloarthritis
  • Most commonly effects the SI joints, cervical spine, thoracic spine, and lumbosacral spine
  • Lower predilection for hips and shoulder joints
  • Spondylitis (inflammation of vertebrae) begins at the insertions of the outer fibers of the annulus fibrosus (enthesitis) of the vertebrae:
    • Ossification (syndesmophyte formation) may lead to complete fusion, ankylosis, of the vertebrae
    • Extensive spinal involvement causes the radiographic appearance of a brittle “bamboo spine”
  • Onset 15–35 yr of age. Almost always before age 45
  • Male to female ratio is between 2:1–3:1
ALERT

AS patients are at 4 times the risk for fracture and paralysis compared to the general population. They are 11 times more likely to have spinal cord injuries

Risk Factors

Genetics

Strong genetic component. HLA-B27 is present in 80–90% of patients with AS

Etiology

Disease is likely triggered by environmental factors such as infection in genetically predisposed individuals

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