What is reactive arthritis?

What is Reactive Arthritis

Reactive arthritis is a sterile inflammatory arthritis that develops 2-4 weeks after a remote infection, typically in the gastrointestinal or urogenital tract, presenting as an asymmetric oligoarthritis predominantly affecting the lower extremity joints. 1, 2

Definition and Pathophysiology

Reactive arthritis represents an aseptic articular inflammation triggered by bacterial infections, most commonly involving:

• Urogenital infections: Chlamydia trachomatis, Ureaplasma urealyticum, Neisseria gonorrhea 3
• Gastrointestinal infections: Salmonella, Shigella, Campylobacter, Yersinia 4, 3

The traditional concept of "sterile" arthritis has been challenged by detection of bacterial DNA, RNA, and metabolically active organisms (particularly Chlamydia) within affected joints, blurring the distinction between reactive and post-infectious arthritis 1, 5

Clinical Presentation

The hallmark features include:

• Acute asymmetric oligoarthritis affecting larger joints, particularly lower extremities 1, 2
• Timing: Develops within 2-4 weeks following the triggering infection 1, 2
• Note: Approximately 25% of patients have asymptomatic preceding infections 1

Associated Features

Reactive arthritis falls under the spondyloarthropathy spectrum and commonly presents with:

• Enthesitis (considered a hallmark finding) 3, 5
• Dactylitis (sausage digits) 4, 5
• Sacroiliitis and axial involvement 4, 5
• Extra-articular manifestations: anterior uveitis, urethritis, skin lesions (pustular plantar lesions) 5

Epidemiology

• Annual incidence: 0.6-27 per 100,000 population 2
• Age: Most common in young adults (18-40 years) 3
• Gender: Post-enteric infections show no significant gender difference; urogenital infections show male predominance (9:1 ratio) 3
• HLA-B27 association: Present in many cases but should not be used as a diagnostic tool for acute reactive arthritis 2

Diagnostic Approach

No validated diagnostic criteria exist; diagnosis is primarily clinical 1, 2. The diagnosis requires:

Essential Elements:

• Clinical pattern: Acute oligoarticular arthritis of larger joints with appropriate timing after infection 1
• Identification of triggering infection through:
  • Stool cultures for enteric pathogens 1
  • Ligase chain reaction for Chlamydia trachomatis 1
  • Serological testing (though not standardized) when cultures are negative 1

Important Caveat:

After arthritis onset, isolating the triggering organism becomes less likely, requiring reliance on serological evidence 1

Distinction from Post-Streptococcal Reactive Arthritis

Post-streptococcal reactive arthritis (PSRA) differs from typical reactive arthritis:

• Timing: Occurs approximately 10 days after streptococcal pharyngitis (earlier than typical reactive arthritis) 6, 7
• Pattern: Cumulative and persistent arthritis involving both large and small joints 6
• Treatment response: Lacks response to salicylates (unlike acute rheumatic fever) 6
• Cardiac risk: May occasionally progress to valvular heart disease, requiring cardiac monitoring per American Heart Association recommendations 6

Prognosis

• Majority: Self-limiting course 5
• 25-50%: Develop recurrent acute arthritis episodes, depending on triggering infection and potential reinfections 1
• 25%: Progress to chronic spondyloarthritis of varying activity 1

Treatment Considerations

• NSAIDs and sulfasalazine: Most commonly used first-line agents 4
• Antibiotics for Chlamydia: Important for active urogenital infection; prolonged treatment may benefit chronic Chlamydia-induced reactive arthritis 2
• Antibiotics for established arthritis: Not effective for curing arthritis from other triggers 1, 2
• DMARDs: Sulfasalazine may be considered for persistent arthritis 6
• TNF-alpha blockers: May be effective in aggressive cases or evolution toward ankylosing spondylitis 4