Definition (J Adolesc Health 2009;44:309; Clin Microbiol Rev 2004;17:348)
• Arthritis associated with a recent, prior, or coexisting extraarticular infection
• Can refer to post-infxn arthritis, urethritis, and conjunctivitis; w/ 3:1 
:
predominance
• Per ILAR; reactive arthritis in pt <16 yo now known as enthesitis-related arthritis
Pathophysiology (Curr Opin Rheumatol 1999;11:238)
• Classic pathogens: Campylobacter, Chlamydia trach, Salmonella, Shigella, Yersinia
• Bacterial antigens in synovium, trigger T-cell resp → immune-mediated synovitis
• Chlamydial DNA and mRNA have been found in synovial membrane biopsies
• Campylobacter, Salmonella, Shigella, Yersinia antigens present in synovial fluid
• 30–70% w/ HLA B27, perhaps because HLA B27 cells allow bacteria to persist
Epidemiology (Clin Microbiol Rev 2004;17:348)
• Uncommon disorder, estimated at 0.1% prevalence; 2nd–4th decade of life
• May be underdiagnosed because of asymptomatic prior infection
• Following GU infxn (male to female 9:1) or enteric infection (male to female 1:1)
Clinical Manifestations (Clin Microbiol Rev 2004;17:348)
• Latent period from infection to onset of symptoms from a few days to 6 wk
• Extraarticular findings include
• Conjunctivitis (30%), often coincides with flares of arthritis, is mild, lasts 1–4 wk
• Urethritis, usually painless, clear discharge; can involve other GU structures
• Dermatologic findings: Balanitis circinata & keratoderma blennorrhagica
• Articular findings: Asym, mono- or oligoarthritis, predominantly lower extremities
Diagnostic Studies (Clin Microbiol Rev 2004;17:348)
• No established diagnostic criteria
• 1996 Third International Workshop on Reactive Arthritis
• Typical peripheral arthritis (predominantly lower limb, asym oligoarthritis)
• Evidence of preceding infection
• If diarrhea or urethritis laboratory confirmation desired, not essential
• If no clinical infection, laboratory confirmation is necessary
• Positive confirmatory testing includes: +stool cx; +chlamydia trachomatis
• Pts w/ other causes (Lyme dz, septic arthritis, spondyloarthritis) are excluded
• Routine HLA B27 screening is not helpful
• Eval: X-rays (usually nml) of affected joints to r/o trauma, joint aspiration to r/o septic arthritis & gout, U/A, Chlamydia PCR, stool cx, Lyme serology, RF, HIV test
Management (Clin Microbiol Rev 2004;17:348)
• NSAIDs (1st line Rx w/ 70–75% response rate), intraarticular corticosteroids, DMARDs (2nd line for refractory arthritis)
• Orthotics for enthesitis if present, gentle ROM exercises and avoidance of overuse
• No controlled data, but sulfasalazine, MTX, azathioprine have shown some efficacy
• Antibiotics: Rx of urethritis can ↓ risk of reactive arthritis and ↓ relapse
• Rx of enteric infections does not affect development of reactive arthritis
Complications (Rheumatology 2000;39:117)
• Most recover in 2–6 mo w/o destructive Δs; 4–19% w/ chronic (>6 mo) arthritis
• Worse prognosis assoc w/: gender, FHx ankylosing spondylitis, presence of HLA B27, ESR > 30, poor response to NSAIDs, onset < 16 yo. (Clin Microbiol Rev 2004;17:348)