Uveitis Does Not Distinguish Ankylosing Spondylitis from Axial Spondyloarthritis
No, acute anterior uveitis does not distinguish ankylosing spondylitis (AS) from non-radiographic axial spondyloarthritis (nr-axSpA)—both conditions are part of the axial spondyloarthritis (axSpA) spectrum and share the same extra-articular manifestations, including uveitis. 1
Understanding the Disease Spectrum
The American College of Rheumatology explicitly states that AS and nr-axSpA are both forms of axSpA, with the primary distinction being the presence or absence of radiographic sacroiliitis—not the presence of extra-articular manifestations like uveitis. 1 The key difference is:
- AS (radiographic axSpA): Advanced sacroiliac joint damage and spine ankylosis visible on radiographs 1
- nr-axSpA: Clinical features of axSpA without radiographic sacroiliitis, though MRI may show inflammation 1
Both conditions share skeletal disease that may be accompanied by uveitis, psoriasis, and inflammatory bowel disease. 1
Uveitis as a Shared Feature
Acute anterior uveitis occurs across the entire axSpA spectrum without distinguishing between AS and nr-axSpA:
- Approximately 40% of AS patients will experience acute anterior uveitis during their disease course 2
- Uveitis is the most common extra-articular manifestation in both AS and nr-axSpA 1, 3
- Recent evidence shows that acute anterior uveitis predicts future development of axSpA in general (odds ratio 4.7; 95% CI 2.2-10.5), but does not differentiate between radiographic and non-radiographic forms 1
Clinical Implications
The presence of uveitis should prompt evaluation for axSpA as a whole, not specifically for AS versus nr-axSpA:
- Among patients presenting with acute anterior uveitis and chronic back pain, approximately 20-40% have undiagnosed axSpA (including both AS and nr-axSpA) 4, 2
- HLA-B27 positivity is common in both AS and nr-axSpA patients with uveitis, but does not distinguish between the two 1
- The distinction between AS and nr-axSpA requires imaging of the sacroiliac joints (radiographs for AS, MRI for nr-axSpA), not clinical features like uveitis 1
Treatment Considerations
The American College of Rheumatology guidelines emphasize that recommendations for AS and nr-axSpA are similar, including management of extra-articular manifestations. 1 For patients with axSpA and uveitis:
- TNF inhibitors (particularly adalimumab and infliximab) are preferred biologic agents for both the axial disease and prevention/treatment of uveitis 1
- The treatment approach does not differ based on whether the patient has radiographic or non-radiographic disease 1
Common Pitfall to Avoid
Do not assume that the presence of uveitis indicates more advanced disease (AS) rather than early disease (nr-axSpA). Uveitis can occur at any stage of axSpA and does not correlate with radiographic progression. 3, 5 The diagnosis of AS versus nr-axSpA must be made through imaging assessment of structural damage, not through the presence or absence of extra-articular manifestations.