Medicine – Triggers of Reactive Arthritis (Reiter’s Syndrome)

Reactive arthritis, previously called Reiter’s syndrome, is a sterile inflammatory arthritis that develops after an infection elsewhere in the body. The triggering infection most commonly involves the genitourinary or gastrointestinal tract. Although the joints become inflamed, the causative organism is generally not present within the joint itself. Symptoms usually begin days to weeks after the initial infection.

1. Chlamydia trachomatis

Chlamydia trachomatis is one of the most important genitourinary triggers of reactive arthritis. The preceding infection may cause urethritis or cervicitis, although it can also be asymptomatic. Reactive arthritis following Chlamydia infection may present with lower-limb arthritis, enthesitis, conjunctivitis, or other mucocutaneous features.

2. Campylobacter jejuni

Campylobacter jejuni is a common gastrointestinal cause of reactive arthritis. It typically produces an episode of acute gastroenteritis with diarrhoea, abdominal pain, and sometimes fever. Joint inflammation may develop after the intestinal symptoms have improved or resolved.

3. Salmonella Species

Salmonella species can also trigger reactive arthritis after gastrointestinal infection. Patients may initially experience diarrhoea, abdominal cramps, and systemic symptoms, followed later by inflammatory joint symptoms. The arthritis is usually asymmetric and tends to involve the lower limbs.

4. Shigella flexneri

Shigella flexneri is another recognised enteric trigger. It causes an acute diarrhoeal illness, often with abdominal cramps and sometimes blood or mucus in the stool. Reactive arthritis can develop afterward as an immune-mediated complication of the infection.

5. Neisseria gonorrhoeae

Neisseria gonorrhoeae has historically been listed among infections associated with post-infectious arthritis. However, an important distinction is that gonococcal infection can also cause true septic arthritis through disseminated gonococcal infection, in which the organism directly infects the joint. Therefore, acute arthritis in the setting of gonorrhoea requires careful assessment to exclude septic arthritis rather than assuming a reactive process.

6. Borrelia burgdorferi

Borrelia burgdorferi, the organism responsible for Lyme disease, has also historically appeared in some lists of infectious triggers. However, Lyme arthritis is generally considered a distinct infectious or post-infectious manifestation of Lyme disease rather than a classic cause of reactive arthritis. It should therefore be differentiated from the more typical reactive arthritis triggered by Chlamydia, Campylobacter, Salmonella, or Shigella.

Key Clinical Concept

The classic infectious triggers of reactive arthritis are Chlamydia trachomatis, Campylobacter jejuni, Salmonella species, and Shigella species. These infections usually affect the genitourinary or gastrointestinal tract, and the subsequent arthritis represents an immune-mediated inflammatory response rather than direct infection of the joint.