Reactive Arthritis

 

• Pathophysiology

  • Post-infectious, autoimmune joint inflammation. A type of peripheral spondyloarthritis (see psoriatic arthritis for more details).
  • Formerly known as Reiter's syndrome.
  • Usually 1-4 weeks post bacterial gastroenteritis – Shigella, Campylobacter, or Salmonella – or STI – chlamydia.

• Signs and symptoms

  Symptoms:

  • Classic triad of conjunctivitis, urethritis, and arthritis: "can't see, can't pee, can't climb a tree".
  • MSK: oligoarthritis of lower limbs, low back pain (50%), enthesitis.
  • Non-articular: conjunctivitis (less commonly, anterior uveitis), mouth ulcers.

  Signs:

  • Circinate balanitis: penile ulcers.
  • Keratoderma blennorrhagica: brown plaques on soles and palms.

• Investigations

  • ↑ESR, ↑CRP.
  • HLA-B27 may help support the diagnosis.
  • Look for recent infection: swabs, stool cultures, serology.
  • Joint aspiration if septic or crystal arthritis is suspected. In reactive arthritis, the joint itself will be sterile, otherwise it's septic.
  • X-ray: enthesitis (e.g. Achilles), sacroiliitis. If X-ray normal, consider US and/or MRI of affected sites.

• Management

  • Stepwise treatment until symptoms controlled: NSAIDs → intra-articular steroids → systemic steroids → sulfasalazine → anti-TNFα (very rare).
  • Antibiotics if there is ongoing infection (especially chlamydia). Does not affect the arthritis.

• Prognosis

  • Most resolve within 6 months.
  • However, relapses may occur (25%), and it can become chronic (10%).