Ankylosing Spondylitis

Question 1

Define

Answer 1

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

Question 2

Causes

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

Epidemiology

Answer 3

COMMON

Earlier presentation in males

Question 4

Symptoms

Answer 4

Gradual onset lower back pain

↘ Worse at night – disturbing sleep

↘ Spinal morning stiffness relieved by exercise

↘ Pain radiates to hips/buttocks

↘ Improved towards the end of the day

• Symptom of asymmetrical peripheral arthritis
• Entheitis – soreness and inflammation swelling
  Achilles tendonitis, plantar fasciitis, at the tibial/ischial tuberosities and at the iliac crests
• ±Fatigue, malaise
• ±Anterior pleuritic mechanical chest pain due to costochondritis
• If untreated – blindness may occur due to acute iritis

Question 5

Signs

Answer 5

Reduced range of spinal movement (particularly hip rotation)

Reduced lateral spinal flexion

Schober’s Test

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

Tenderness over the sacroiliac joints

LATER STAGES:

• Thoracic kyphosis
• Spinal fusion
• Question mark posture

Signs of Extra-Articular Disease: 5 As

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

Question 6

Investigations

Answer 6

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 margins

LATER STAGES:

• Erosions
• Sclerosis
• Sacroiliac joint fusion

CXR - check for apical lung fibrosis

Lung Function Tests

• Assess mechanical ventilatory impairment due to kyphosis