Axial Spondyloarthritis

Axial spondyloarthritis (axSpA) is the umbrella term for chronic inflammatory disease of the sacroiliac joints and spine, comprising non-radiographic axSpA and radiographic axSpA (ankylosing spondylitis).

• Prevalence 0.7 to 1.4%; non-radiographic and radiographic disease occur in roughly equal numbers, with women more often non-radiographic.

• 10 to 12% of non-radiographic patients progress to radiographic disease over 2 years (more with high CRP, MRI inflammation, HLA-B27, smoking).

• Overlaps with psoriasis, IBD, uveitis, and peripheral features (enthesitis, dactylitis).

• Diagnostic delay averages 5 to 8 years.

• Chronic back pain over 3 months, onset before age 45, with inflammatory features: morning stiffness, relief by exercise, nocturnal pain, alternating buttock pain.

• Enthesitis, dactylitis, peripheral oligoarthritis, anterior uveitis.

• Fatigue, sleep disturbance, reduced spinal mobility in later disease.

• ASAS classification: sacroiliitis on imaging plus one SpA feature, or HLA-B27 plus two features.

• MRI sacroiliac joints (active inflammation: subchondral bone marrow oedema on STIR, extending 2 consecutive slices); radiographs for structural change.

• HLA-B27, CRP; exclude mechanical back pain, diffuse idiopathic skeletal hyperostosis, osteitis condensans ilii, infection, fracture.

• Assess disease activity with ASDAS and BASDAI, function with BASFI.

• Education, structured exercise, physiotherapy, smoking cessation.

• NSAIDs at full dose for 4 weeks: naproxen 500 mg twice daily, etoricoxib 60 to 90 mg daily, diclofenac 75 mg twice daily; continue if effective.

• Active disease (ASDAS 2.1 or more) despite 2 NSAIDs: biologic.

• TNF inhibitor: adalimumab 40 mg every 2 weeks, etanercept 50 mg weekly, certolizumab 200 mg every 2 weeks, or golimumab 50 mg monthly.

• IL-17 inhibitor: secukinumab 150 mg, ixekizumab 80 mg every 4 weeks, or bimekizumab 160 mg every 4 weeks.

• JAK inhibitor: upadacitinib 15 mg daily or tofacitinib 5 mg twice daily.

• Non-radiographic disease responds similarly, with objective inflammation (CRP or MRI) predicting better response.

• Conventional DMARDs for peripheral arthritis only. Steroid injections for enthesitis or sacroiliac joints.

• If remission sustained for over 6 months, dose reduction (extended interval) can be attempted.

• Bone health, cardiovascular risk management, vaccinations.