Ankylosing spondylitis

Question 1

What is ankylosing spondylitis?

Answer 1

A spondyloarthropathy associated with the HLA-B27 gene
Chronic, multi-system inflammatory disorder

Inflammation of the sacroiliac joints and axial skeleton that presents as chronic back pain, morning stiffness, and eventually spinal deformity in long-standing cases.

Question 2

Causes of disease

Answer 2

Complex interaction between genetic make-up, gut microbiome, immune response, and mechanical stress at typical anatomical sites

The strongest genetic contribution is linked to HLA-B27, which is one of the major histocompatibility complex (MHC) Class I molecules

Question 3

Epidemiology of AS? Risk factors ?

Answer 3

Male to female ratio is 3:1
Teens- mid-thirties
(95% of patients will present before 45 years)

Risk factors: positive family history of AS and being HLA-B27-positive

Question 4

Symptoms ?

Answer 4

• Back pain(inflammatory pattern- worse with inactivity/morning, improves with exercise): sacroiliac and spinal involvement
• Morning stiffness >30 mins
• chest wall and thoracic pain
• Bilateral buttock pain
• Fatigue
• Arthritis

Question 5

Signs on examination?

Answer 5

May be normal

Later disease:
- Loss of lumbar spine lordosis, exaggerated thoracic kyphosis
- Reduced chest expansion
- Schober’s test- Positive (mark skin 10cm above and 5cm below PSIS, bend forward with straight legs and distance increase to >20cm is normal )
- Enthesitis(inflammation at the insertion of tendons and ligaments)

Question 6

What is Schober’s test?

Answer 6

Mark skin 10cm above and 5cm below PSIS, bend forward with straight legs and distance increase to >20cm is normal
In AS decreased lumbar spine flexion seen

Question 7

What are the extra-articular manifestations?

Answer 7

• Iritis/ Anterior uveitis: inflammation of the middle layer of the eye (i.e. the uvea). Typically causes unilateral eye pain, redness, and photophobia.
• Atlanto-axial instability: increases risk of cord compression
• Aortitis: can lead to aortic regurgitation
• Atrioventricular block
• Apical lung fibrosis
• Amyloidosis: secondary to chronic inflammation
• IgA nephropathy

Question 8

What investigations can we do ?

Answer 8

• Pelvic and spinal X-Ray
• MRI Spine and SI joints- if X ray normal and to see enthesitis
• Routine bloods (for medications used) and CRP, ESR
• HLA-B27

Question 9

What can you see on pelvic X-ray ?

Answer 9

• Sacroiliitis may be unilateral or bilateral and is graded from 1 to 4 depending on the severity

Question 10

On later stage spinal X rays what may be seen

Answer 10

Bamboo spine- vertebral body fusion by marginal syndesmophytes and squaring of the vertebral bodies. Gives the impression of a continuous lateral spinal border on x-rays like a bamboo stem.
Dagger sign- ossification of the supraspinous and interspinous ligaments leading to a central radiodense line running up the spine

Question 11

What criteria is used for diagnosing AS?

Answer 11

Modified New York Criteria classification for AS

Question 12

What is the criteria for the Modified New York Criteria classification?

Answer 12

Diagnosis

• Definite ankylosing spondylitis: radiological criterion is present plus at least 1 clinical criterion
• Probable ankylosing spondylitis: if EITHER radiological criterion OR 3 clinical criteria are present alone

Clinical criteria

• Low back pain ≥ 3 months, improved by exercise and not relieved by rest
• Limitation of the lumbar spine in sagittal and frontal planes
• Limitation of chest expansion (relative to normal values corrected for age and sex)

Radiological criterion

• Bilateral grade 2-4 sacroiliitis OR unilateral grade 3-4 sacroiliitis

Question 13

Management: non-pharmacological and pharmacological

Answer 13

• Patient education
• Smoking cessation
• Psychological support
• Physiotherapy: exercise has been shown to improve disease activity in AS
• NSAIDS
• Biologics- Anti-TNF and IL-17 inhibitors

Conventional DMARDS less used as ineffective against axial involvement

Question 14

Complications

Answer 14

• Spinal fusion: limits mobility
• Osteoporosis- 1/3 of pts with AS
• Spinal fractures: higher risk as the disease progresses (up to 10%)
• Restrictive lung disease: due to apical fibrosis and thoracic cage abnormalities
• Spinal cord injury: due to fractures or stenosis
• Cardiac disease: valvular disease, heart failure, arrhythmias
• Kyphoscoliosis (e.g. ankylosing spondylitis) can cause a restrictive lung defect on spirometry
• Restrictive lung disease: due to apical fibrosis and thoracic cage abnormalities