Ankylosing spondylitis (MSK) Flashcards
What is ankylosing spondylitis?
Seronegative spondyloarthropathy and a chronic inflammatory disease of the axial skeleton that leads to partial or complete fusion and rigidity of the spine
Describe the epidemiology of ankylosing spondylitis.
Young males:
- M>F
- 15-40y
What gene is ankylosing spondylitis associated with?
HLA-B27
What condition is ankylosing spondylitis associated with?
IBD - Crohn’s and UC
What conditions make up seronegative spondyloarthropathy? (4)
- ankylosing spondylitis
- psoriatic arthritis
- reactive arthritis
- enteropathic arthritis (IBD-associated)
What is the difference between axial spondyloarthritis and ankylosing spondylitis?
- axial spondyloarthritis is a chronic progressive inflammatory arthropathy which can ultimately lead to radiographical changes in the spine and sacroiliac joints
- this radiographical stage is known as ankylosing spondylitis (AS)
Describe the pathophysiology of ankylosing spondylitis.
- chronic autoimmune (against type I+II collagen) inflammatory disease that affects vertebral joints
- over time the inflammation destroys the intervertebral joints, facet and sacroiliac joints, and fibroblasts replace the destroyed joints with fibrin
- layers of fibrin form a tough fibrous band around the outside of joints –> limited ROM + bamboo spine
- eventually osteoblasts are activated and ossification starts when fibrous tissue turns to bone
What are syndesmophytes (ankylosing spondylitis)?
Small bony outgrowths form at the joint edges = syndesmophytes (vertical ossifications bridging the margins between adjacent vertebrae –> immobility) + cause bony joint fusion (ankylosis)
How do vertebral bodies look in ankylosing spondylitis?
Become more square
What is the hallmark clinical feature of ankylosing spondylitis?
Inflammatory back pain - insidious onset, early morning stiffness which improves with activity, worse when resting (at night)
What are the clinical features of ankylosing spondylitis?
- inflammatory back pain - early morning stiffness/pain which improves with activity +/- night pain
- anterior uveitis/iritis - eye pain, redness, photophobia
- enthesitis - inflammation where tendon/ligament attaches to bone (Achilles most common site)
- tenderness at sacroiliac joint
- reduced spinal mobility + ROM
- constitutional symptoms - fatigue, weakness, fever, WL
- extra-articular features (6A’s)
What extra-articular features are seen in ankylosing spondylitis? (6A + 2)
- Apical lung fibrosis
- Amyloidosis
- Anterior uveitis
- Achilles tendinitis (heel pain)
- Aortic regurgitation
- AV node block
- (Cauda equina syndrome)
- (Peripheral Arthritis)
How does anterior uveitis present in ankylosing spondylitis? (3)
- eye pain
- redness
- photophobia
What constitutional features are seen in ankylosing spondylitis? (4)
- fatigue
- weakness
- fever
- weight loss
What might be found on examination in ankylosing spondylitis? (5)
- reduced range of spinal movement (especially hip flexion)
- reduced lateral spinal flexion
- reduced forward spinal flexion (Schober’s test)
- tenderness over sacroiliac joints
- reduced chest expansion
What is Schober’s test (ankylosing spondylitis)?
Line drawn 10cm above and 5cm below the back dimples - distance between the two lines should increase by >5cm when patient bends as far forward as possible (reduced movement suggests ankylosing spondylitis)
What does Schober’s test show in ankylosing spondylitis?
Reduced forward flexion <5cm
How does ankylosing spondylitis present in later stages? (3)
- thoracic kyphosis
- spinal fusion
- question mark posture
What are some risk factors for ankylosing spondylitis? (4)
- male (3:1)
- HLA-B27
- IL23R and ERAP1
- Fx
What is the first-line investigation for ankylosing spondylitis?
Pelvic X-ray (requested in all patients presenting with inflammatory back pain)
What does pelvic XR show in ankylosing spondylitis?
Sacroiliitis –> subchondral erosions and sclerosis
What will lumbar XR show in ankylosing spondylitis? (2)
- bamboo spine - syndesmophytes (ossification of outer fibres of annulus fibrosus) form between adjacent vertebrae
- squaring of lumbar vertebrae
What investigations are done in ankylosing spondylitis? (6)
- pelvic XR (1st line)
- lumbar XR
- HLA-B27 (+ve but not diagnostic)
- MRI
- CXR + spirometry
- Schober’s test (reduced forward flexion <5cm)
When do we do MRI in ankylosing spondylitis?
- if high suspicion for AS but XR negative
- may show enthesitis
