Table of Contents
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)
- Schober’s test: mark midline 10cm above the dimples of Venus and 5cm below while standing, then re-measure distance in flexion (<5cm difference implies lumbar flexion limitation that may be due to ankylosing spondylitis)
- <5cm chest circumference expansion on inspiration
Extra-articular features
- Extra-articular features: A
- 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)
Management
- Exercise and physiotherapy: essential
- NSAIDs (e.g. ibuprofen, naproxen, diclofenac): may need to try two or more
- TNF-α inhibitors (e.g. etanercept) may be used when two or more NSAIDs have failed
- 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