Peripheral Spondyloarthritis

Peripheral spondyloarthritis (pSpA) is spondyloarthritis dominated by peripheral arthritis, enthesitis or dactylitis, without predominant axial involvement.

• Classified by ASAS: arthritis (usually asymmetric, lower limb) or enthesitis or dactylitis, plus one SpA feature (preceding infection, HLA-B27, uveitis, psoriasis, IBD, sacroiliitis on imaging) or two other features.

• Includes reactive arthritis, psoriatic, enteropathic, and undifferentiated forms.

• Prevalence is lower than axial disease; younger adults, often HLA-B27 positive.

• Course ranges from self-limiting to chronic erosive disease.

• Asymmetric oligoarthritis of knees, ankles, feet, with dactylitis and heel pain.

• Enthesitis at Achilles, plantar fascia, patellar tendon, iliac crest.

• Uveitis, psoriasis, gut symptoms, preceding infection.

• Axial symptoms may develop later.

• Clinical assessment of joint count and entheses; inflammatory markers; HLA-B27.

• Ultrasound or MRI to confirm enthesitis and synovitis; radiographs for erosions; MRI sacroiliac joints to detect axial involvement.

• Exclude gout, septic arthritis (aspiration), rheumatoid arthritis, osteoarthritis, Lyme disease.

• Screen for psoriasis, IBD, STI/GI infection triggers.

• NSAIDs first line (naproxen 500 mg twice daily, celecoxib 200 mg daily), local steroid injection (triamcinolone 20 to 40 mg), orthotics and physiotherapy for enthesitis.

• Conventional DMARDs if persistent: sulfasalazine 2 to 3 g daily (best evidence), methotrexate 15 to 25 mg weekly, leflunomide 20 mg daily.

• Biologics for failure: TNF inhibitors (adalimumab, etanercept, certolizumab, golimumab), IL-17 inhibitors (secukinumab, ixekizumab) unless IBD is active.

• Treat triggers (chlamydia with doxycycline 100 mg twice daily for 7 days).

• Short oral prednisolone 15 to 30 mg for flares, tapered quickly.

• Uveitis or IBD association: favour monoclonal TNF inhibitors.

• Review at 3 months; treat to target remission.