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Annual incidence for acute reactive arthritis is conservatively estimated between 1/11,000-166,000, although this may be an underestimate. The prevalence of the chronic form is unknown. The disease most commonly affects young adults and is associated with HLA-B27 allele, especially in its chronic form.

Age of onset varies widely, with a peak at 15-35 years of age. The disease usually occurs within 1-3 weeks after a urogenital or gastrointestinal infection. Urinary symptoms are often the first manifestation. Prostatitis in men, and cervicitis, salpingitis and/or vulvovaginitis in women are frequent findings. Arthritis generally appears several weeks or months after the initial symptoms. It often affects one (knee) or a few major joints (knees, ankles or toes). The tendons and ligaments next to the joints may also be inflamed, particularly the Achilles tendon and the lower back joints. Extraarticular manifestations may involve the eye with conjunctivitis, iritis, or uveitis, as well as the skin with rashes on the hands or feet. Balanitis, nail changes, mucosal ulcers, fever, weight loss, and cardiac manifestations may also occur. In most patients, the symptoms last for 1-6 months, but the disease can also become chronic.

Reactive arthritis is typically triggered by Gram-negative infections (commonly due to Chlamydia, Shigella, Salmonella, or Yersinia) in genetically predisposed individuals.

The diagnosis relies on a compatible clinical scenario and history, the identification of a trigger infection and is supported by HLA-B27 positivity.

Differential diagnosis includes other spondyloarthritis (ankylosing spondylitis, psoriatic arthritis, inflammatory bowel disease-associated spondyloarthropathy, juvenile-onset spondyloarthropathy, and undifferentiated spondyloarthropathy). Septic arthritis, gonococcal infection, and viral arthritis should also be excluded.

Genetic testing for HLA-B27 is not recommended in the absence of a clinical suspicion.

Management aims at eradication of the underlying infection (antibiotics) and reduction of joint pain and inflammation (analgesics, anti-inflammatory drugs, steroids and immunosuppressants), as well as rest and specific treatment of extraarticular manifestations.

Prognosis is variable. One-third of patients may develop chronic disease which requires prolonged or life-long treatment. However, the majority of patients have a normal life span and nearly normal lifestyle.