Ankylosing spondylitis

Question 1

Define Ankylosing Spondylitis

Answer 1

Chronic progressive inflammatory seronegative arthropathy

Question 2

Aetiology of Ankylosing Spondylitis

Answer 2

Genetic component (heritability 97%): HLA-B27 (90% of patients +) ± ERAP1, ARTS1

Inflammation at the entheses (ligamental attachments) → fibroblasts replace the joint with fibrin → fibrous band → limited range of motion → new bone formation (ossification)
→ vertebral body squaring
→ syndesmophyte formation (vertebral ossifications) + fusion
- Calcification of spinal ligaments

Question 3

Epidemiology of Ankylosing Spondylitis

Answer 3

Commonly presents in the second decade of life (18-25)
Men more frequently affected than women (2.5:1)

Question 4

Symptoms of Ankylosing Spondylitis

Answer 4

Back pain: worse in morning | better on exercise | worse with rest | insidious onset | >3 months
Morning stiffness
Loss of spinal movement
Asymmetrical peripheral arthritis
Sleep disturbance
Dyspnoea, pleuritic chest pain (costovertebral involvement, pulmonary fibrosis)
Heel pain (caused by plantar fasciitis/enthesitis)
Malaise, fatigue
IBD, osteoporosis

Question 5

Signs of Ankylosing Spondylitis on examination

Answer 5

MSK
Reduced range of spinal movements (particularly hip rotation)
Reduced lateral spinal flexion and occiput-wall distance (patient standing next to wall)
Loss of lumbar lordosis
Kyphosis
Enthesitis: tenderness at joints (usually lower limb e.g. heel, knee, tuberositis)
In later stages, thoracic kyphosis and spinal fusion, question-mark posture.

Schober’s test:
- A mark is made on the skin of the back in the middle of a line drawn between the posterior iliac spines.
- A mark 10 cm above this is made.
- The patient is asked to bend forward and the distance between the two marks should expand by >5 cm on forward flexion.
- This is reduced in ankylosing spondylitis.

Signs of extra-articular disease:
Anterior uveitis/iritis (red eye, painful, blurring of vision)
Apical lung fibrosis
Aortic regurgitation (cardiac diastolic murmur).
Reduced chest expansion (fusion of costovertebral joints)

Question 6

Investigations for Ankylosing Spondylitis

Answer 6

Graded via “New York” criteria
Refer to rheumatology for confirmation

Urine dip: ?amyloidosis
Bloods: HLA-B27, ESR/CRP

XR pelvis: Sacroiliitis (unilateral or bilateral)
- Corner erosions
- Syndesmophytes
- Sclerosis
- Ankylosis (fusion)
- Bamboo spine (squaring of lumbar vertebrae)
- ‘Dagger’ sign = supraspinous tendon ossification
MRI: bone marrow oedema, erosion or narrowing of joint spaces
XR spine: erosions, squaring, sclerosis, syndesmophytes, bamboo spine
Echo: ?Aortic regurgitation
HRCT: ?pulmonary fibrosis

Question 7

Managament for Ankylosing Spondylitis

Answer 7

Refer to rheumatology, in the meantime: NSAIDs
Conservative (exercise/physiotherapy)
- Dry land physiotherapy and hydrotherapy
- Bath ankylosing spondylitis disease activity index (BASDAI)
- Medical
1. NSAID e.g. naproxen 500mg PO BD
2. NSAID
3. Anti-TNFa (etanercept)
4. Secukinumab
- Surgical (hip replacement to ↓ pain and ↑ mobility)

Note
Anterior uveitis suspected (red and acutely painful ± blurred vision or photophobia) → urgent ophthal referral

Question 8

Complications for Ankylosing Spondylitis

Answer 8

Ankylosis or spinal fusion
Spinal fractures (rate up to 10%)
Hip involvement
Anterior uveitis
Osteoporosis
Cardiovascular complications e.g. valvular disease, arrhythmias, heart failure
Lung: restrictive pulmonary disease, fibrosis

Question 9

Prognosis for Ankylosing Spondylitis

Answer 9

Variable course, often fluctuating axial inflammation + structural
Prognosis of ankylosing spondylitis also depends on the presence of extraspinal manifestations (for example uveitis, psoriasis, inflammatory bowel disease), the person’s age at diagnosis, and the choice of treatment progression
Risk of spinal fracture increases later in life due to osteoporosis → fragility fractures