Reactive Arthritis

Reactive arthritis is a sterile inflammatory arthritis triggered by a distant infection, typically genitourinary or enteric.

• Onset 1 to 4 weeks after infection. Triggers: Chlamydia trachomatis, Salmonella, Shigella, Yersinia, Campylobacter, rarely Clostridioides difficile.

• 60 to 85% are HLA-B27 positive. Males and young adults are more affected after genital infection.

• Classic triad (Reiter): arthritis, urethritis, conjunctivitis.

• Most resolve in 3 to 12 months; 15 to 30% develop chronic arthritis or evolve into spondyloarthritis.

• Asymmetric oligoarthritis of lower limbs (knee, ankle), dactylitis, enthesitis (Achilles, plantar fasciitis), sacroiliitis.

• Urethritis, cervicitis, balanitis circinata, painless oral ulcers, keratoderma blennorrhagicum (soles).

• Conjunctivitis, anterior uveitis.

• Fever and malaise; preceding diarrhoea or dysuria may have resolved.

• Clinical, with synovial fluid: inflammatory, culture negative, crystals absent.

• CRP and ESR raised, HLA-B27, rheumatoid factor negative.

• Identify trigger: urine or swab NAAT for chlamydia and gonorrhoea, stool culture and PCR, serology for Yersinia/Campylobacter if needed. Test HIV, hepatitis B/C, syphilis.

• Exclude septic arthritis (aspiration), gout, psoriatic arthritis, gonococcal arthritis, Lyme disease.

• NSAIDs: indomethacin 25 to 50 mg three times daily, naproxen 500 mg twice daily, for weeks to months.

• Intra-articular triamcinolone 20 to 40 mg for monoarthritis. Prednisolone 20 to 30 mg for severe polyarticular disease, tapered.

• Treat active chlamydia infection: doxycycline 100 mg twice daily for 7 days (partner treatment); antibiotics for other bacterial triggers help only the infection, with limited effect on arthritis. Prolonged antibiotic courses are not recommended.

• Persistent arthritis over 3 months: sulfasalazine 1 g twice daily (up to 3 g), methotrexate 15 to 25 mg weekly; TNF inhibitors (adalimumab 40 mg every 2 weeks) for refractory or axial disease.

• Uveitis: topical prednisolone 1% drops hourly, cycloplegic, ophthalmology.

• Physiotherapy; safe sex counselling and screening for other infections.