Ankylosing Spondylitis

Snapshot

• A 21-year-old man presents to his physician’s clinic with lower back pain. He reports the pain is accompanied by stiffness, is worse in the morning, and improves with exercise. He denies any radiation of pain or bowel and bladder incontinence. On physical exam, there is decreased anterior flexion of the lumbar spine. Laboratory testing is positive for HLA-B27. A plain radiograph of the spine is shown. 

Introduction

• Clinical definition
  • chronic inflammatory disorder that primarily affects the sacroiliac joint and spine
• Epidemiology
  • demographics
    • more common in men
    • peak onset age is 15-35 years of age
  • risk factors 
    • HLA-B27 gene presence
• Etiology
  • unknown but may involve both genetic (e.g., HLA B-27 positivity) and environmental factors
• Pathogenesis
  • unclear but involves inflammation, bone erosion, and spur formation
    • can result in spinal fusion and costovertebral and costosternal
      ankylosis
  • involves the entheses
    • connective tissue between bone and a tendon or ligament
• Associated conditions
  • psoriasis
  • inflammatory bowel disease
  • anterior uveitis 
  • aortic regurgitation
• Prognosis
• may lead to chronic pain and stiffness

Presentation

• Symptoms 
  • back pain
    • worse in the morning and lasts approximately 30 minutes
    • pain improves with activity
  • stiffness of the spine
  • anterior uveitis
    • photophobia
    • watering and redness of the eye
• Physical exam
  • may have stooped posture
  • positive Schober test
    • demonstrates limited spine flexibility
• decreased chest wall expansion

Imaging

• Radiography
  • indication
    • gold standard for evaluating and supporting the diagnosis of ankylosing spondylitis
  • findings
• “bamboo spine” 

Studies

• Labs
  • HLA-B27 positivity
• seen in > 90% of patients

Differential

• Mechanical low back pain
• Enteropathic arthritis
• Reactive arthritis
• Psoriatic arthritis

Treatment

• Conservative
  • patient education and exercise
    • indication
      • mainstay of treatment
• Medical
  • nonsteroidal antiinflammatory drugs (NSAIDs)
    • indication
      • considered first-line treatment for managing pain and stiffness
  • tumor necrosis factor (TNF) inhibitors
    • indication
      • typically used in patients who do not respond to conservative and NSAID treatment
    • medications
      • adalimumab
• etanercept

Complications

• Low bone density
• Spine fracture leading to injury of the spinal cord
• Restrictive lung disease