Ankylosing spondylitis

Ankylosing spondylitis is a chronic seronegative spondyloarthropathy which primarily involves the axial skeleton.

Risk factors

• HLA-B27 (positive in 90-95%)
• Age: peak onset 15-25 years
• Male gender
• Family history

Clinical features

Symptoms

• Low back pain
  • Progressive
  • Relieved by exercise
  • Night pain
  • Radiates to sacroiliac joints and hips
• Morning stiffness 
• Systemic features: fever, weight loss, fatigue

Signs

• Question mark posture (loss of lumbar lordosis and thoracic kyphosis)
• Sacroiliac joint tenderness (sacroiliitis)
• Positive Schober’s test
• <5cm chest circumference expansion on inspiration 

Extra-articular features

• Anterior uveitis
• Aortitis
• Aortic regurgitation
• AV node block
• Apical pulmonary fibrosis
• Amyloidosis → glomerulonephritis
• Achilles tendon (and other tendon) enthesitis

Investigations

• Clinical diagnosis
• X-Rays: pelvis and spine (‘bamboo spine’ is a characteristic sign caused by vertebral body fusion by marginal syndesmophytes)
• MRI: more sensitive than X-Ray
• Bloods: FBC (anaemia), ESR (raised), CRP (raised), HLA B27 (+ve)

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Management

• Exercise and physiotherapy: essential
• NSAIDs (e.g. ibuprofen, naproxen, diclofenac): may need to try different ones
• TNF-α inhibitors (e.g. etanercept) may be used when NSAIDs are unsuccessful or not tolerated
• Interleukin-17A inhibitors (e.g. secukinumab): may be used in place of TNF-α inhibitors
• Other therapies: corticosteroid joint injections, short courses of corticosteroids, intravenous bisphosphonates

Reference: NICE ‘NG65: Spondyloarthritis in over 16s: diagnosis and management’ 2017

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