Ankylosing Spondylitis

Basics

Description

Chronic inflammatory disease, primarily affects the axial skeleton with predilection toward the spine and sacroiliac (SI) joints:
- SI joints 100%
- Cervical spine 75%
- Thoracic spine 70%
- LS spine 50%
- Hip joints 30%
- Shoulder joints 30%
Spondylitis (inflammation of vertebrae) of ankylosing spondylitis (AS) begins at the insertions of the outer fibers of the annulus fibrosus (enthesitis) of the vertebrae:
- Ossification (syndesmophyte formation) may lead to complete fusion, ankylosis, of the vertebrae
- Extensive spinal involvement causes the radiographic appearance of the brittle “bamboo spine”
Onset 15–35 yr of age. Rarely after age 45
Male to female ratio is between 2:1–3:1

ALERT
AS patients are at 4 times the risk for fracture and paralysis compared to the general population. They are 11 times more likely to have spinal cord injuries

Risk Factors

Genetics
Strong genetic component. HLA-B27 is present in 80–90% of patients with AS

Etiology

Disease is likely triggered by environmental factors such as infection in genetically predisposed individuals

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