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.