Reactive arthritis (formerly known as Reiter syndrome) is a postinfectious autoimmune condition that is most commonly preceded by bacterial infection of the gastrointestinal or urinary tract. It is categorized as a seronegative spondyloarthropathy and is associated with HLA-B27. Reactive arthritis often affects young adults and manifests with musculoskeletal and/or extraarticular symptoms. The classic triad of arthritis, conjunctivitis, and urethritis is only seen in about one-third of patients. The diagnosis is based on clinical features such as patient history and physical examination and may be supported by laboratory or imaging findings, although there are no specific confirmatory tests for reactive arthritis. Reactive arthritis usually resolves spontaneously within 6–12 months; treatment during this acute phase is primarily supportive (e.g., NSAIDs for arthritis). Underlying infections should be identified and treated. A small proportion of patients develop severe or chronic arthritis; for these individuals, systemic corticosteroids or disease-modifying antirheumatic drugs (DMARDs) may be required.
Postinfectious autoimmune disorder 
- Posturethritis: after infection with Chlamydia (common) or Ureaplasma urealyticum
- Postenteritis: after infection with Shigella, Yersinia, Salmonella, or Campylobacter 
- In rare cases: after infection with Bartonella henselae 
She Cherishes Cooking Yummy Salmon: Shigella, Chlamydia, Campylobacter, Yersinia, and Salmonella are the most common causes for reactive arthritis.
- Latency period: 1–4 weeks
- Musculoskeletal symptoms
- Conjunctivitis, iritis, episcleritis, or keratitis
- Dermatologic manifestations ; 
- Oral ulcers
- Cardiac manifestations 
- Symptoms from preceding infection
- Reactive arthritis is primarily a clinical diagnosis. 
- Laboratory studies and imaging typically show nonspecific signs of inflammation.
- Further studies may be necessary to:
Laboratory studies 
- Blood tests: Consider in all patients although findings are often nonspecific.
- Arthrocentesis with synovial fluid analysis: indicated if the diagnosis is unclear or if there is a concern for septic arthritis 
- Stool culture: Perform only in ongoing diarrhea; send culture for Shigella, Yersinia, Salmonella, and Campylobacter.
- STI testing: indicated for patients with
As with other seronegative arthropathies, there is an association between reactive arthritis and HLA-B27 (approximately 50–80% of HLA-B27 tests are positive in patients with reactive arthritis); however, HLA-B27 testing is not required to diagnose reactive arthritis and does not change the management of the condition. 
- Suspected arthritis
- Suspected synovitis or enthesitis
- Suspected cardiac manifestations
- Suspected ocular manifestations: slit lamp examination for keratitis and anterior uveitis
- Acute reactive arthritis
- Chronic reactive arthritis (i.e., persistence of symptoms > 6 months) or severe disease: DMARDs (e.g., sulfasalazine) may be required.
NSAIDs: first-line treatment for all symptomatic patients 
- Choose medication based on patient characteristics; start with a high dose and titrate to the lowest effective dose. 
- See “Oral analgesics” for further information, including dosages.
- Glucocorticoids: indicated in patients with inadequate response or
- DMARDs: indicated in patients with chronic (> 6 months) or severe disease 
Extraarticular manifestations 
Treatment should be overseen by the relevant specialist.
- Ocular 
- Dermatologic: Treatment typically involves topical steroids and keratolytics.
Management of underlying infections 
- Treat active infections.
- Treat all patients with (even if asymptomatic).
- Consider treatment for patients with severe immunocompromised.  , especially if
- For sexually transmitted infections:
- Report to the relevant state and/or national authorities.
Infection-associated arthritis 
|Differential diagnoses of infection-associated arthritis |
|Nongonococcal||Gonococcal (disseminated gonococcal infection) |
|Risk factors|| |
|Onset|| || || || || |
|Distribution pattern|| || |
Non-infectious arthritis 
The differential diagnoses listed here are not exhaustive.
- Resolves spontaneously within a year
- High rate of recurrence