Enthesitis, HLA-B27 and the IL-23/IL-17 axis in spondyloarthritis
Why spondyloarthritis starts at the enthesis, what HLA-B27 does and what a positive test is worth (worked Bayes), how IL-23 and IL-17 drive skin, joint and new bone, and why IL-23 blockers fail in the spine while IL-17 blockers worsen Crohn disease.
Tier 2Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- Spondyloarthritis (axial SpA, psoriatic arthritis, reactive arthritis, enteropathic arthritis and anterior uveitis) is a family of diseases centred on the enthesis, not the synovium.
- Autoantibodies are absent. Disease comes from innate and IL-23/IL-17-driven immunity at sites of mechanical stress and barrier surfaces: skin, gut and eye.
- HLA-B27 is the strongest genetic risk but most carriers stay well.
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Sources
- Therapeutic Guidelines: Rheumatology (spondyloarthritis)AU/NZTherapeutic Guidelines Limited (eTG complete), current online version, accessed November 2026
- Ramiro S et al. ASAS-EULAR recommendations for the management of axial spondyloarthritis: 2022 update. Ann Rheum Dis 2023;82:19-34ASAS and EULAR, 2022 update
- Sherlock JP et al. IL-23 induces spondyloarthropathy by acting on ROR-gamma-t+ CD3+CD4-CD8- entheseal resident T cells. Nat Med 2012;18:1069-76Nature Medicine, 2012
- Baeten D et al. Secukinumab, an interleukin-17A inhibitor, in ankylosing spondylitis (MEASURE 1 and MEASURE 2). N Engl J Med 2015;373:2534-48New England Journal of Medicine, 2015
- Baeten D et al. Risankizumab, an IL-23 inhibitor, for ankylosing spondylitis: results of a randomised, double-blind, placebo-controlled, proof-of-concept, dose-finding phase 2 study. Ann Rheum Dis 2018;77:1295-302Annals of the Rheumatic Diseases, 2018
- Hueber W et al. Secukinumab, a human anti-IL-17A monoclonal antibody, for moderate to severe Crohn's disease: unexpected results of a randomised, double-blind placebo-controlled trial. Gut 2012;61:1693-700Gut, 2012
- Schett G, Lories RJ, D'Agostino MA et al. Enthesitis: from pathophysiology to treatment. Nat Rev Rheumatol 2017;13:731-41Nature Reviews Rheumatology, 2017
- Last updated
- 14 November 2026
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