How does reactive arthritis typically occur?

Reactive arthritis commonly occurs as a sequela to a prior infection, particularly those involving the gastrointestinal or genitourinary tracts. This type of inflammation arises due to the immune system's response to pathogens, such as certain bacteria, that have triggered an infectious episode. Examples of bacteria associated with reactive arthritis include Chlamydia trachomatis, which is linked to genitourinary infections, as well as Salmonella, Shigella, and Campylobacter that are known to cause gastrointestinal infections.

The hallmark of reactive arthritis is that it typically arises weeks to months following the initial infection, highlighting the delayed nature of the immune response. Patients often present with unilateral joint pain and swelling, particularly in the lower extremities, which is distinct from the arthritis seen with directly infectious causes where joints are inflamed due to a direct infectious agent.

Understanding the relationship between preceding infections and the development of reactive arthritis is crucial for diagnosis and management. This connection allows clinicians to investigate recent symptoms suggestive of infection to identify any underlying associations that may have led to the inflammatory condition.