Ankylosing spondylitis
Ankylosing spondylitis is the radiographic axial spondyloarthritis: a chronic, HLA-B27-associated inflammatory disease of the sacroiliac joints, spine, and entheses presenting with inflammatory back pain before age 45. Sacroiliitis on pelvic radiograph or MRI establishes the diagnosis. First-line treatment is continuous scheduled NSAIDs with active exercise, escalating to a tumor necrosis factor inhibitor, then an interleukin-17 inhibitor, when NSAIDs fail.
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What this article covers
- Overview
Definition: ankylosing spondylitis is the radiographic form of axial spondyloarthritis, a chronic inflammatory disease of the sacroiliac joints, spine, and entheses (tendon and ligament insertions…
- Epidemiology
Prevalence tracks HLA-B27: 0.32% in North America versus 0.07% in Africa; male-to-female ratio about 2 to 3:1.
- Risk factors
HLA-B27 positivity: the dominant genetic risk factor, though insufficient alone, since only about 6% of HLA-B27-positive White individuals ever develop disease; interleukin-23 receptor polymorphisms…
- Pathophysiology
Genetic susceptibility: HLA-B27 presents antigen to CD8 T cells and is strongly associated with axial involvement.
- Clinical features
Inflammatory back pain defines the presentation: insidious low back and buttock pain and stiffness over 3 months, beginning before age 45, worse at night and in the morning, improved by exercise but…
- Differential diagnosis
Psoriatic arthritis: axial disease can occur, but more often starts as asymmetric peripheral or distal interphalangeal (DIP)-predominant arthritis with psoriatic skin and nail changes and bulkier…
- Diagnosis
The diagnosis is established by the Assessment of Spondyloarthritis International Society (ASAS) criteria: back pain over 3 months with age at onset under 45, plus either sacroiliitis on radiography…
- Management
First, continuous scheduled NSAIDs plus active exercise and physical therapy; continuous, not as-needed, dosing is the only regimen shown to slow new bone formation here.
- Complications
Vertebral fracture through a rigid, fused spine: fractures after minor trauma, through the vertebral body or a syndesmophyte-fixed disk space, causing nerve injury or myelopathy; osteoporosis, common even early, adds to this risk.
- Prognosis
TNF inhibitors are uniquely disease-modifying in ankylosing spondylitis among the spondyloarthritides, with trial evidence of clinical, radiographic, and MRI improvement.
- Prevention
Use continuous, not on-demand, NSAID dosing in active disease, the regimen associated with slowed radiographic progression.
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Psoriatic arthritis (PsA) is a seronegative spondyloarthritis that develops in up to 30% of patients with psoriasis, producing asymmetric oligoarthritis or distal interphalangeal joint disease, dactylitis, enthesitis, nail dystrophy, and axial involvement. Diagnosis is clinical, supported by the CASPAR criteria. Limited peripheral disease is treated with an NSAID or intra-articular glucocorticoid, more active disease with methotrexate, a tumor necrosis factor inhibitor, or an interleukin-17 inhibitor.
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Uveitis is inflammation of the uveal tract, classified by anatomic location as anterior, intermediate, posterior, or panuveitis and by systemic association such as HLA-B27 spondyloarthritis, sarcoidosis, or Behcet disease. Anterior uveitis presents with a painful red eye and photophobia diagnosed at the slit lamp, while posterior uveitis presents with painless floaters or vision loss, and treatment is topical corticosteroid for anterior disease escalating to systemic corticosteroid and steroid-sparing immunosuppression for recurrent, severe, or posterior-segment disease.