Reactive arthritis, also known as Reiters syndrome, is a form of inflammatory arthritis that develops in response to an infection in another part of the body (cross-reactivity). Coming into contact with bacteria and developing an infection can trigger the disease. By the time the patient presents with symptoms, often the "trigger" infection has been cured or is in remission in chronic cases, thus making determination of the initial cause difficult. The arthritis often is coupled with other characteristic symptoms; this has been called Reiters syndrome, Reiters disease or Reiters arthritis. The term "reactive arthritis" is increasingly used as a substitute for this designation because of Hans Reiters war crimes with the Nazi Party. The manifestations of reactive arthritis include the following triad of symptoms: an inflammatory arthritis of large joints, inflammation of the eyes in the form of conjunctivitis or uveitis, and urethritis in men or cervicitis in women. Arthritis occurring alone following sexual exposure or enteric infection is also known as reactive arthritis. Patients can also present with mucocutaneous lesions, as well as psoriasis-like skin lesions such as circinate balanitis, and keratoderma blennorrhagicum. Enthesitis can involve the Achilles tendon resulting in heel pain. Not all affected persons have all the manifestations. The clinical pattern of reactive arthritis commonly consists of an inflammation of fewer than five joints which often includes the knee or sacroiliac joint.
Other urogenital problems may arise such as prostatitis in men and cervicitis, salpingitis and/or vulvovaginitis in women. It presents with monoarthritis affecting the large joints such as the knees and sacroiliac spine causing pain and swelling. An asymmetrical inflammatory arthritis of interphalangeal joints may be present but with relative sparing of small joints such as the wrist and hand. Patient can have enthesitis presenting as heel pain, Achilles tendinitis or plantar fasciitis, along with balanitis circinata (circinate balanitis), which involves penile lesions present in roughly 20 to 40 percent of the men with the disease. A small percentage of men and women develop small hard nodules called keratoderma blennorrhagicum on the soles of the feet and, less commonly, on the palms of the hands or elsewhere. The presence of keratoderma blennorrhagica is diagnostic of reactive arthritis in the absence of the classical triad. Subcutaneous nodules are also a feature of this disease. Ocular involvement (mild bilateral conjunctivitis) occurs in about 50% of men with urogenital reactive arthritis syndrome and about 75% of men with enteric reactive arthritis syndrome. Conjunctivitis and uveitis can include redness of the eyes, eye pain and irritation, or blurred vision. Eye involvement typically occurs early in the course of reactive arthritis, and symptoms may come and go. Dactylitis, or "sausage digit", a diffuse swelling of a solitary finger or toe, is a distinctive feature of reactive arthritis and other peripheral spondylarthritides but can also be seen in polyarticular gout and sarcoidosis. Mucocutaneous lesions can be present.