Pocket Pediatrics: The Massachusetts General Hospital for Children Handbook of Pediatrics (Pocket Notebook Series), 2 Ed.

REACTIVE (ENTHESITIS-RELATED) ARTHRITIS

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

• CampylobacterSalmonella, 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)