1+ Ankylosing Spondylitis

Question 1

What is ankylosing spondylitis?

Answer 1

A chronic inflammatory disease of the spine and sacroiliac joints that leads to partial or complete fusion and rigidity of the spine

Question 2

What is the epidemiology of AS?

Answer 2

M>F
15-40 yo
Onset is BEFORE 40, often begins in 30s

Question 3

What is the aetiology of SpA?

Answer 3

Likely genetic
- HLA-B27
- Lots of other genes seem to contribute (HLA-B60)

But environmental interplay

Question 4

What is the pathophysiology of AS?

Answer 4

1. Fluctuating inflammation
2. Erosive damage + repair
3. New bone formation/osteoproliferation –> syndesmophytes so spine progressively stiffens

Question 5

What are the characteristics of the back pain in AS?

Answer 5

• Insidious onset before 40
• Duration of back pain longer than 3 months
• Morning stiffness
• Decreased pain with exercise
• Good response to NSAIDs

Question 6

What are the extra-skeletal featutes of AS?

Answer 6

• Anterior uveitis
• CVS involvement
• Pul involvement e.g. fibrosis
• Cauda equina syndrome
• Enteric mucosal lesions
• Amyloidosis

Question 7

What are the skeletal features of AS?

Answer 7

Skeletal:
- Axial arthritis= sacroiliitis and spondylitis
- Arthritis of the girdle joints
- Peripheral arthritis UNCOMMON
- Other: enthesitis, OP, vertebral fractures

Question 8

What are the features of AS on examination?

Answer 8

• Decreased spinal ROM in all directions
• Loss of lumbar lordosis (increased kyphosis)
• Neck hyperextension (occiput to wall test and tragus to wall)
• Modified Schober’s test (<5cm)
• Lateral spinal flexion reduced
• Tenderness over sacroiliac joint
• Reduced chest expansion

Question 9

How can you monitor AS?

Answer 9

• Number of joints
• Stiffness duration
• CRP and ESR
• Fatigue with BASDAI

Question 10

What Ix do you do for AS?

Answer 10

Biochemical:
- Increased CRP and ESR
- RF, ANA, Anti-ccp negative
- HLA-B27 positive

Imaging:
- Not always required by X-RAY
- Sacroiliitis: sclerosis, erosions, joint space widening, ankylosis
- Spine: loss of lordosis, straightening of the spine, syndesmophytes (bamboo spine)

Question 11

What is the pharmacological management of AS?

Answer 11

1. NSAIDs
2. Biologic DMARDs: TNFalpha inhibitors (infliximab, entanercept, adalimumab)
3. Other biologics: secukinumab (IL-17 inhibitor)

Traditional DMARDs and steroids are really only for peripheral arthritis and DONT help axial SpA

Question 12

What is the role of HLA-B27/theories of aetiology in ankylosing spondylitis?

Answer 12

Canonical:

1. AI arthritogenic peptide
2. HLA-B27 is poor at clearing infections so you have chronic immune stimulation

Non-Canonical:
3. HLA-B27 forms homodimers, there is heavy chain misfolding in the ER –> proinflammatory unfolded protein response –> IL-23 release which activates T cells at enthesis (ankylosing) + activates Th17 to release IL-17 which makes the T cell produce pro-inflammatory cytokines –> inflammation

4. HLA-B27 is an autoantigen

Question 13

What are the two types of ‘predominantly axial’ SpA?

Answer 13

1. Non-radiographic axial SpA
   - IBP
   - Sacroilitis on MRI
2. Ankylosing Spondylitis
   - IBP
   - Sacroiliitis on X-Ray

Question 14

How does the inflammation of RA and AS differ?

Answer 14

RA = persistent –> just get erosions

AS= fluctuating –> inflammation –> repair –> syndesmophytes

Question 15

Summary of Ankylosing Spondylitis

Answer 15

Male
<40
Insidious onset
Sacroiliitis and spondylitis = 100%
Peripheral joints only 25%
HLA-B27 = 97%
Eye: anterior uveitis
Cardiac
Pulmonary