Reactive Arthritis

Introduction

• Reactive arthritis, formerly known as Reiter's syndrome, is a term used to refer to the appearance of rheumatologic disease following an infection
• It is called "reactive" because the musculoskeletal complaints are triggered by an autoimmune reaction to the initial infection

Pathogenesis

• Some GI infections can produce arthritic symptoms
  • Yersinia
  • Camplobacter
  • Salmonella
  • Chlamydia
  • Shigella
• The incidence of arthritis after an acute attack of dysentery is reported to be between 2 – 33%
• The HLA-B27 phenotype in particular, seems to predispose to reactive arthritis following Yersinia infection
• HLA-B27 genotype has been reported in up to 90% of reactive arthritis due to Yersinia infection
• E. coli has also been noted to produce an arthritic picture, but no connection between HLA-B27 and the subsequent development of reactive arthritis has been found

Natural History

• Reactive arthritis is an uncommon disease
  • Prevalence estimated at 30-40 per 100,000 adults
  • Annual incidence 5-28 per 100,000
• It is more prevalent in Scandinavian populations; in fact, most studies on reactive arthritis are conducted in Scandinavian populations
• Most cases are sporadic, but there have been outbreaks reported with specific strains of each pathogen
• The peak age is the 3rd and 4th decades
• The condition is more common in white, male patients

Clinical Presentation

• Typically, the arthritis will develop between 2 - 3 weeks following the GI infection
• Sacroiliitis is present in 25% of patients, but more asymmetric than in Ankylosing Spondylitis
• Usually affects large joints
  • The knee, ankle, wrist, and sacroiliac joints are commonly involved
  • The typical arthritis pattern is lower extremity dominant
  • Asymmetrical
  • Mono/oligo-articular pattern
• Associated findings
  • Enthesitis (insertional tendinopathy)
    • Enthesitis can present as sausage like digits and swelling of the heels
    • The insertions of the Achilles tendon and the plantar fascia on the calcaneus are commonly involved
  • Ocular involvement
    • Conjuctivitis
    • Anterior uveitis
  • Urethritis
    • May be sterile
    • Can present with dysuria and increased frequency of urination
    • Skin or genital rash may be seen

Differential Diagnosis

• Chlamydia or Gonnococal infection may cause urethritis
• Analyzing synovial fluid for culture and crystal involvement is important to rule out septic arthritis and gout

Imaging and other Diagnostic Studies

X-Ray

• Initially normal, then shows erosive arthropathy
• Vertebral changes similar to Ankylosing Spondylitis
• Sacroiliitis
• Periosteal changes in
  • Ischial tuberosity
  • Greater trochanter
  • Site of insertion of Achilles tendon

Laboratory tests

• Only 50% of patients with reactive arthritis will be HLA-B27 positive
• The genotyping test is usually reserved in highly suspect circumstances  

Treatment

• Treat the underlying infection
• Provide palliation for the reactive symptoms

Outcome

• The prognosis depends on
  • The strain of pathogen
  • Genetic and environmental factors
• Overall prognosis is good, with the arthritis remitting in < 6 months
• Only 4 - 10% of patients in one Finland study had reactive arthritis that lasted >1 year. Their reactive arthritis was induced by strains of either Yersinia, Salmonella, Shigella or Chlamydia
• Importantly, the presence of HLA-B27 does not seem to correlate with either the severity or the duration of the disease
• It was noted that patients who develop reactive arthritis following a GI infection are more likely to develop other auto-immune associated conditions like psoriasis, ankylosing spondylitis, and inflammatory bowel disease later in life

Related Topics

• The triad of "Can't see; can't pee; can't bend my knee" suggests reactive arthritis
• German physician Hans Reiter first described reactive arthritis and gives his name to the eponym
• Reactive arthritis is a so-called "seronegative spondylarthropathy" in that it appears similar to rheumatoid arthritis; i.e. it's a "spondylarthropathy", but the rheumatoid factor test is negative; hence "seronegative"

References