Ankylosing spondylitis

Question 1

Define ankylosing spondylitis

Answer 1

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

Question 2

Explain the aetiology/risk factors of ankylosing spondylitis

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

Pathophysiology
Inflammation starts at the entheses, (where ligaments attach to vertebral bodies)
Persistent inflammation leads to reactive new bone formation

Changes begin in the lumbar vertebrae and progress superiorly
Vertebral bodies become more square
Syndesmophytes (vertical ossifications bridging the
margins between adjacent vertebrae)
Fusion of syndesmophytes and facet joints
Calcification of anterior and lateral spinal ligaments

Question 3

Summarise the epidemiology of ankylosing spondylitis

Answer 3

COMMON

Earlier presentation in males

Question 4

Recognise the presenting symptoms of ankylosing spondylitis

Answer 4

Lower back and sacroiliac pain
Disturbed sleep

Pain pattern
Worse in the morning
Better with activity
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 5

Recognise the signs of ankylosing spondylitis on physical examination

Answer 5

Reduced range of spinal movement (particularly hip rotation)

Reduced lateral spinal flexion

Positive Schober’s Test

Tenderness over the sacroiliac joints

LATER STAGES:
Thoracic kyphosis
Spinal fusion
Question mark posture

Question 6

Signs of Extra-Articular Disease

Answer 6

5As

Anterior uveitis
Apical lung fibrosis
Achilles tendinitis
Amyloidosis
Aortic regurgitation

Question 7

Identify appropriate investigations for ankylosing spondylitis

Answer 7

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

Radiographs
Anteroposterior and lateral radiographs of the spine - May show Bamboo spine
Anteroposterior radiograph of sacroiliac joints - Shows symmetrical blurring of joint margin

LATER STAGES:
Erosions
Sclerosis
Sacroiliac joint fusion

CXR - check for apical lung fibrosis

Lung Function Tests - Assess mechanical ventilatory imp
airment due to kyphosis