Overview
Definition
A chronic inflammatory arthritis (seronegative spondyloarthropathy) primarily affecting the axial skeleton (spine and sacroiliac joints), leading to eventual fusion (ankylosis).
Epidemiology
Typically affects young males (onset in late teens or 20s).
Etiology & Risk Factors
- Strong genetic association with the HLA-B27 allele.
- Inflammation occurs at the entheses (where tendons/ligaments attach to bone).
Clinical Symptoms
- Inflammatory back pain: Insidious onset, worse in the morning (severe stiffness), IMPROVES with exercise and activity, wakes patient up in the second half of the night
- Sacroiliitis (alternating buttock pain)
- Extra-articular: Anterior Uveitis (red, painful eye with photophobia - most common extra-articular manifestation)
Clinical Approach
Diagnosis
- X-ray of Sacroiliac (SI) joints: Shows sacroiliitis (sclerosis, erosions). This can take years to show up.
- MRI of SI joints: Best test for early, active inflammation (osteitis/bone marrow edema)
- Spine X-ray (Late finding): 'Bamboo spine' (fusion of the vertebral bodies via syndesmophytes)
Management
- First-line: NSAIDs (Indomethacin, Naproxen) at continuous, high doses PLUS regular physical therapy/exercise
- Second-line (for axial disease refractory to NSAIDs): TNF-alpha inhibitors (Etanercept, Adalimumab, Infliximab) or IL-17 inhibitors (Secukinumab)
- Note: Traditional DMARDs like Methotrexate do NOT work well for axial (spine) disease
Complications
- Spinal fusion leading to severe kyphosis and loss of mobility
- Restrictive lung disease (due to fusion of the costovertebral joints preventing chest expansion)
- Aortic regurgitation