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Reactive arthritis

Definition and Epidemiology

  • Reactive arthritis (formerly known as Reiter’s syndrome) is an inflammatory arthritis that develops in response to an infection in another part of the body.
  • Typically occurs after gastrointestinal or genitourinary infections.
  • More common in males aged 20-40 years and those with the HLA-B27 genotype.

Pathophysiology

  • Arises as a reaction to an infection, but the bacteria are not found in the affected joints.
  • Common triggering infections include Chlamydia trachomatis (sexually transmitted) and certain gastrointestinal pathogens (Salmonella, Shigella, Campylobacter, Yersinia).
  • The exact mechanism is unclear, but it is thought to involve an abnormal immune response to the infection, particularly in genetically susceptible individuals.

Clinical Features

  • Onset of symptoms typically occurs 1-4 weeks after the triggering infection.
  • Classic triad: arthritis, conjunctivitis, and urethritis.
  • Arthritis is usually asymmetric, affecting knees, ankles, and feet.
  • Enthesitis (inflammation at sites where tendons insert into the bone) and dactylitis (sausage digits) may occur.
  • Extra-articular manifestations include skin lesions (keratoderma blennorrhagicum) and mucocutaneous lesions.

Diagnosis

  • Based on the clinical presentation and a history of recent infection.
  • Laboratory tests: Elevated inflammatory markers (ESR, CRP), negative rheumatoid factor and ANA, indicating a non-autoimmune arthritis.
  • Synovial fluid analysis: typically shows inflammatory arthritis but sterile culture.
  • Screening for underlying genitourinary or gastrointestinal infection.

Management

  • Treatment of the underlying infection with appropriate antibiotics.
  • NSAIDs for symptomatic relief of arthritis.
  • Intra-articular corticosteroids or systemic corticosteroids for severe or refractory cases.
  • Physical therapy to maintain joint function and mobility.

Complications

  • Chronic joint pain and arthritis in a minority of cases.
  • Recurrent episodes, especially in individuals with untreated chronic infections or HLA-B27 positivity.
  • Uveitis and other ocular complications.

Prognosis

  • Generally good, with most patients recovering fully within 3-12 months.
  • Some may develop chronic arthritis or recurrent episodes.

Prevention

  • Prevention of triggering infections through safe sexual practices and proper food handling.
  • Early treatment of symptomatic infections to reduce the risk of developing reactive arthritis.

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