Reactive arthritis is an inflammatory disease that develops in response to a gastrointestinal or urinary tract infection.
It is characterized by non-suppurative joint inflammation that appears after an infection elsewhere in the body, primarily intestinal or genital.
Reactive arthritis is a rheumatic disease previously known as Reiter’s syndrome.
Reactive arthritis results from a combination of environmental and genetic factors.
It often appears after gastrointestinal or genital infections caused by bacteria such as Salmonella, Shigella, Yersinia, Campylobacter, and Chlamydia trachomatis. Cases related to Clostridioides difficile, Mycoplasma, and Neisseria gonorrhoeae have also been described.
After infection, an autoimmune reaction is triggered, leading to inflammation of the joints, mainly in the synovial membrane and at the entheses (where tendons or ligaments attach to bone). Less frequently, the skin and mucous membranes may also be affected.
A key genetic factor is HLA-B27. Carriers of this marker have a higher risk of developing more severe forms of the disease. For example, in Yersinia-induced reactive arthritis, HLA-B27–positive individuals more often present with urethritis, mucocutaneous manifestations, and low back pain compared with those without this marker.
It should be noted that in about 25% of cases, no preceding infection can be identified.
The prevalence of reactive arthritis is estimated at 30–40 cases per 100,000 people, and the annual incidence at 5–28 cases per 100,000 people.
It mainly affects adults between 20 and 40 years of age.
Reactive arthritis occurs in 1–3% of patients with an intestinal or genitourinary infection, except in yersiniosis, where it develops in 10–33% of cases.
Following gastrointestinal infection, it affects men and women equally, whereas after genitourinary infection, it is more frequent in men (ratio 9:1).
It is more common in patients with HIV infection.
Symptoms usually begin 1 to 4 weeks after a genitourinary or gastrointestinal infection.
Reactive arthritis is characterized by the following triad:
The full triad is not always present.
Additional symptoms may include:
There is no specific test for reactive arthritis. Diagnosis is based on clinical symptoms, disease progression, a history of infection, and exclusion of other causes.
Reactive arthritis is suspected in patients with peripheral arthritis lasting more than one month, accompanied by urethritis and/or cervicitis.
Recommended tests include a complete blood count, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), serological or PCR tests for Chlamydia, stool cultures, and imaging studies (ultrasound or MRI), depending on the extent of involvement.
Treatment depends on the stage of the disease.
If the infection is still active, antibiotics are prescribed; however, bacterial eradication does not always resolve joint inflammation.
Otherwise, physical therapy and nonsteroidal anti-inflammatory drugs (NSAIDs) are the main treatment measure.
Swimming is particularly recommended, while contact sports should be avoided.
NSAIDs are an essential part of therapy; commonly used agents include indomethacin, diclofenac sodium, naproxen, and ibuprofen.
Steroids have shown limited efficacy, but intra-articular corticosteroids may be used in persistent cases.
Disease-modifying antirheumatic drugs (DMARDs), such as sulfasalazine and methotrexate, are reserved for chronic or persistent forms, especially when multiple joints are affected or there is a risk of joint damage.
In refractory patients, biological agents such as tumor necrosis factor (TNF) inhibitors or interleukin inhibitors (anti–IL-6, anti–IL-17) may be considered.
The first episode typically lasts an average of 19 weeks, ranging from 2 weeks to over 12 months; in 60–70% of cases, it resolves within 6 months.
Although often self-limiting, up to 30–50% of patients develop chronic disease with alternating periods of remission and relapse.
Urethral infections are not detected in 42% of relapses; therefore, they are best described as relapses rather than new episodes.
When ocular involvement occurs initially, it tends to recur. Long-term follow-up shows that uveitis is uncommon in the early years and usually appears after 5–10 years.
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