Ankylosing Spondylitis

Question 1

Definition

Answer 1

SERONEGATIVE inflammatory arthropathy affecting preferentially the axial skeletal and
large proximal joints

Question 2

Aetiology

Answer 2

• UNKNOWN
• Strong association with the HLA-B27 gene (> 90% of cases are HLA-B27 positive)
• Infective triggers and antigen cross-reactivity with self-peptides have been
hypothesised

Question 3

Pathophysiology

Answer 3

o Inflammation starts at the entheses (where ligaments attach to vertebral bodies)
o Persistent inflammation leads to reactive new bone formation
o Changes begin in the lumbar vertebrae and progress superiorly
o Vertebral bodies become more square
o Syndesmophytes (vertical ossifications bridging the margins between adjacent
vertebrae)
o Fusion of syndesmophytes and facet joints
o Calcification of anterior and lateral spinal ligaments

Question 4

Epidemiology

Answer 4

• COMMON

* Earlier presentation in males

Question 5

Presenting symptoms

Answer 5

• Lower back and sacroiliac pain
• Disturbed sleep

• Pain pattern
o Worse in the morning
o Better with activity
o Worse when resting

• Progressive loss of spinal movement
• Symptoms of asymmetrical peripheral arthritis
• Pleuritic chest pain (due to costovertebral joint involvement)
• Heel pain (due to plantar fasciitis)
• Non-specific symptoms (e.g. malaise, fatigue)

Question 6

Signs on physical examination

Answer 6

• Reduced range of spinal movement (particularly hip rotation)
• Reduced lateral spinal flexion
• Tenderness over the sacroiliac joints

• LATER STAGES:
o Thoracic kyphosis
o Spinal fusion
o Question mark posture

Question 7

Presenting symptoms (extra-articular disease)

Answer 7

o Anterior uveitis
o Apical lung fibrosis
o Achilles tendinitis 
o Amyloidosis
o Aortic regurgitation

Question 8

Schober’s test

Answer 8

o Two fingers are placed on the patients back about 10 cm apart
o The patient is asked to bend over
o The distance between the two fingers should increase by > 5 cm on forward flexion
o Reduced movement would suggest ankylosing spondylitis

Question 9

Investigations (scans)

Answer 9

Radiographs

o Anteroposterior and lateral radiographs of the spine
• May show Bamboo spine

o Anteroposterior radiograph of sacroiliac joints
• Shows symmetrical blurring of joint margins

o LATER STAGES:
• Erosions
• Sclerosis
• Sacroiliac joint fusion

o CXR - check for apical lung fibrosis

Question 10

Investigations (other)

Answer 10

Bloods
o FBC - anaemia of chronic disease
o Rheumatoid factor - negative
o ESR/CRP - high

Lung Function Tests
o Assess mechanical ventilatory impairment due to kyphosis