Formerly known as Reiter syndrome, the classic triad of spondyloarthritis-related symptoms includes arthritis, nongonococcal urethritis, and conjunctivitis. Associated with HLA-B27, it can often follow an infection (Chlamydia trachomatis or pneumonia, Yersinia, Salmonella, Shigella, Campylobacter, or Clostridium difficile). Superficial oral and penile ulcers are not uncommon.

Diagnosis starts with laboratory testing to confirm a preceding or ongoing enteric or genitourinary infection, and to exclude other causes of mono- or oligoarticular arthritis. There is no single definitive test. The prognosis is usually good with most patients recovering spontaneously. In addition to treating any infection, NSAIDs (naproxen 500 mg three times daily or indomethacin 50 mg three times daily) may help as well. For those who don't respond to NSAIDs, intraarticular injections of glucocorticoids may be used. Completely refractory patients may be started on a trial of sulfasalazine (beginning with 500 mg twice daily and increasing, as tolerated to 1000 mg twice daily) or a trial of etanercept (50 mg subcutaneously weekly).