Excerpt from Reactive Arthritis

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Background

Reactive arthritis (also referred to as Reiter syndrome) identifies a constellation of clinical findings classically described as the triad of noninfectious urethritis, arthritis, and conjunctivitis, but, perhaps, this syndrome is better described as a triad of arthritis, conjunctivitis or iridocyclitis, and nonbacterial urethritis or cervicitis.

Reactive arthritis is classified as a seronegative spondyloarthropathy. Seronegative spondyloarthropathies are a group of diseases with a negative rheumatoid factor. Diseases include ankylosing spondylitis, reactive arthritis, inflammatory bowel disease, and psoriatic arthritis. These disorders are characterized by spondylitis or sacroiliitis; peripheral joint disease; and, commonly, an increased incidence of the histocompatibility locus antigen B27 (HLA-B27). They also have a high incidence of associated ocular inflammatory disease.

Pathophysiology

Reactive arthritis exists in 2 forms: epidemic and endemic.

Epidemic reactive arthritis occurs after an infectious gram-negative gastroenteritis, dysentery, or nongonococcal urethritis. The ensuing sterile arthritis occurs after the gastroenteritis has resolved. The associated nongonococcal urethritis organisms include Chlamydia trachomatis and Ureaplasma urealyticum.

In a recent study looking at 2299 participants after a mean follow-up of 4.5 years after an outbreak of Escherichia coli O157:H7 and Campylobacter species within a regional drinking water supply, "arthritis was reported in 15.7% of participants who had been asymptomatic during the outbreak, and in 17.6% and 21.6% of those who had moderate and severe symptoms of acute gastroenteritis, respectively (P-value for trend = 0.009). Compared with the asymptomatic participants, those with moderate and severe symptoms of gastroenteritis had an adjusted relative risk of arthritis of 1.19 (95% confidence interval [CI] 0.99-1.43) and 1.33 (95% CI 1.07-1.66), respectively."¹ So, the risk of reactive arthritis appears to be correlated to the severity of symptoms during the initiating episode.

While a triggering agent can be identified for epidemic reactive arthritis, none has been identified for endemic reactive arthritis. Although differentiation between the 2 types may be difficult in some cases, it is not essential to either the diagnosis or the treatment. Because patients with reactive arthritis often develop urethritis and present to venereal disease clinics, endemic reactive arthritis was initially believed to be due to a venereal disease. The agent most often linked to endemic reactive arthritis was Chlamydia; however, careful studies have not demonstrated a higher prevalence of chlamydial infection in patients with reactive arthritis compared with controls.

Frequency

United States

The incidence reported in US Navy personnel over a 10-year period was 4 cases per 100,000 men per year. Of patients with nongonococcal urethritis, 1-3% develop reactive arthritides, and probably 20-25% of patients with HLA-B27 also develop reactive arthritides. Reactive arthritis may occur in 1.5% of Shigella enterocolitis cases and 25% of HLA-B27–positive Shigella cases.

International

Frequency is probably similar to that seen in the United States.

Race

No known racial difference in either the incidence or the severity of the disease exists.

Sex

This condition is more commonly identified in males, but it may occur more frequently in females than previously believed.

Age

• Onset of the clinical disease occurs in young adults aged 16-40 years.
• Reactive arthritis is infrequent in children.

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