Ankylosing Spondylitis

Question 1

Define ankylosing spondylitis

Answer 1

Chronic progressive inflammatory seronegative arthropathy

Question 2

Aetiology of Ankylosing Spondylitis

Answer 2

Genetic component - HLA B-27, ERAP1, ARTS1

Inflammation, cartilage erosion and subsequent repair (ossification)

Associated with psoriasis and IBD (10%)

RF: family history, klebisella pneumoniae

Question 3

Epidemiology of ankylosing spondylitis

Answer 3

Commonly presents in the 2nd decade of life
Men more frequently affected than women (2:1)
Delay of diagnosis from symptom onset of about 8 years

Question 4

Presenting symptoms of ankylosing spondylitis

Answer 4

Inflammatory back pain (morning back stiffness which improves with activity and returns on rest | Insidious onset | lasts >3 months)

Progressive loss of spinal movement 
Sleep disturbance
Sacroiliac joint tenderness
Costovertebral involvement: dyspnoea, pleuritic chest pain
Plantar fasciitis -> heel pain
Malaise, fatigue

Question 5

Signs of ankylosing spondylitis

Answer 5

Schober’s test - mark made half way between the posterior iliac spines + a mark 10cm above this. Distance reduced (<5cm) when the patient is asked to bend forward

Reduced range of spinal movement, esp. hip 
Reduced lateral spinal flexion 
Loss of lumbar lordosis
Enthesitis (heel, knee etc.)
Kyphosis
(psoriasis, IBD)

Later: Thoracic kyphosis, spinal fusion, question mark posture

Question 6

What extra-articular manifestations can occur in ankylosing spondylitis

Answer 6

Reduced chest expansion (fusion of costovertebral joints)
Anterior uveitis/iritis (red eye)
Apical lung fibrosis
Aortic regurgitation (cardiac diastolic murmur)

Question 7

Investigations for ankylosing spondylitis

Answer 7

Pelvic XR: Sacroiliitis, uni/bilateral

HLA-B27: +/-

MRI: Bone marrow oedema on STIR image, Erosion or narrowing joint spaces (early), joint fusion (late)

Cervical, lumbar and thoracic spine XR: Erosions, squaring, sclerosis, (bridging) syndesmophytes (bony spurs), bamboo spine (late, calcification of spinal ligaments), corners of vertebral body erosion (Romanus Lesion)

USS: enthesitis