FFinalistSouthampton · 2027
Musculoskeletal
AKT · Musculoskeletal/Inflammatory arthritis

Ankylosing spondylitis

HLA-B27-associated axial seronegative spondyloarthropathy (sacroiliitis → spinal fusion)

Overview

A chronic seronegative spondyloarthropathy causing inflammatory axial pain and progressive fusion of the spine and sacroiliac joints. Typically a young man with inflammatory back pain (worse with rest, better with exercise, prolonged morning stiffness) and HLA-B27 positivity. The extra-articular 'A's (anterior uveitis, aortic regurgitation, apical lung fibrosis) are high-yield.

Recognise

  • Young man with insidious inflammatory back pain/buttock pain >3 months: worse with rest and at night, BETTER with exercise, morning stiffness >30 min
  • Reduced lumbar flexion (Schober test), reduced chest expansion, 'question-mark' posture; enthesitis (Achilles/plantar), dactylitis
  • Extra-articular 'A's: Anterior uveitis (commonest), Aortic regurgitation, Apical lung fibrosis, AV block, Amyloidosis, IBD association

Red flags

  • Acute anterior uveitis (painful red eye, photophobia) → same-day ophthalmology
  • Spinal fracture risk in a fused, osteoporotic 'bamboo' spine after minor trauma → low threshold for imaging

Differentials & how to tell them apart

Mechanical back painworse with activity, relieved by rest, no inflammatory features or sacroiliitis
Other spondyloarthropathies (psoriatic/reactive/enteropathic)associated psoriasis, infection trigger, or IBD
Diffuse idiopathic skeletal hyperostosis (DISH)flowing ossification, older patient, no sacroiliitis/inflammation
'Bamboo spine' — syndesmophytes fusing the spine in ankylosing spondylitis (X-ray)

'Bamboo spine' — syndesmophytes fusing the spine in ankylosing spondylitis (X-ray)

Stevenfruitsmaak / CC BY-SA 3.0 — Wikimedia Commons

Investigations

X-ray of sacroiliac joints (sacroiliitis — erosions, sclerosis, fusion; 'bamboo spine' and syndesmophytes late); MRI SI joints for early disease (bone-marrow oedema); HLA-B27; raised ESR/CRP; reduced chest expansion / Schober test.

Management

Exercise/physiotherapy + NSAIDs first-line; anti-TNF/IL-17 if inadequate

  1. 1Confirm with SI-joint imaging (X-ray; MRI for early sacroiliitis) and HLA-B27. First-line = a structured exercise/physiotherapy programme plus NSAIDs.Gate: Axial disease does NOT respond to conventional DMARDs (methotrexate/sulfasalazine) — those are only for peripheral joints; escalate axial disease to a biologic.
  2. 2Persistent active disease despite NSAIDs → anti-TNF or IL-17 inhibitor. Manage extra-articular disease (uveitis, AR); maintain bone health and posture.
Regular exercise/physiotherapy + NSAIDs — cornerstone — NSAIDs are first-line drug therapy and physio maintains mobility
Anti-TNF or IL-17 inhibitor (secukinumab) — for active disease despite NSAIDs (axial disease doesn't respond to conventional DMARDs)
Conventional DMARDs (sulfasalazine) for peripheral joints only — do not help axial disease
Treat extra-articular disease — uveitis (ophthalmology), monitor for AR/conduction disease

Key points

Young man + inflammatory back pain (better with exercise, worse with rest) + HLA-B27 + sacroiliitis = ankylosing spondylitis → exercise + NSAIDs, biologic if refractory. Remember the 'A's (anterior uveitis, AR, apical fibrosis). DMARDs don't help the spine.

Monitor & prognosis

BASDAI disease activity, spinal mobility, screen for uveitis/AR; bone density.

Variable; early treatment and exercise preserve function; advanced disease fuses the spine.

Source: NICE NG65 (spondyloarthritis)