Reiter's syndrome is another name for reactive arthritis, although the latter is being used more commonly now. Genitourinary infections with organisms such as Chlamydia and gastrointestinal infections such as with Salmonella are known to be associated with the incidence of this condition. HLAB27, a human leucocyte antigen, which is well known to be associated with the condition ankylosing spondylitis, is also connected with reactive arthritis and places it with AS in the conditions called seronegative spondyloarthropathies. Urethritis and conjunctivitis are common findings in these conditions but the arthritis can occur without them.
Reactive arthritis typically comes on two to four weeks after a gastrointestinal or a genitourinary infection, with a prior respiratory infection from Chlamydia also a possible trigger. Around ten percent of arthritis onsets do not have an obvious infection preceding the joint problems. Inflammation of many body areas can be involved such as the joints, the connections between the ligaments, tendons and bone, the spinal regions, the skin, gastro-intestinal tract, eyes and mucous membranes. Anyone who is HLAB27 positive has a 50 times increased likelihood of developing reactive arthritis, and on average 75% of reactive arthritis suffers are HLA positive.
Longer lasting and more damaging arthritis is suffered by those patients who are HLAB27 positive or have a strong familial tendency to this condition. From 1 to 4 percent of those suffering a gut related infection may develop reactive arthritis but this number varies greatly even with the same infecting agent. How the biological agent and the person's body react to cause the arthritis is not known and none of the infecting agents are found in the joint fluids. Immune reaction to the infectious agents does occur and antibodies have been isolated from joint fluids, suggesting this might be an immune mediated inflammatory condition.
The self limiting nature of this kind of arthritis means that the condition settles down over a 3-12 month period whether the severity of the symptoms is greater or lower. The chance of the condition recurring is significant, with a higher incidence if a patient is positive for HLAB27, and a new episode is potentially triggered by infections or other agents. The arthritic process can be mild or can cause destructive and disabling changes in the joints in a small group of fifteen percent of sufferers. The usual age range for onset of this condition is between 20 and 40 years, gut infections giving a 50:50 male to female ratio and urogenital infections giving a 9 to 1 ratio.
There is usually an acute and sudden onset of reactive arthritis and patients typically exhibit fatigue, fever and malaise with arthritis of a few joints in the lower extremity in a non-symmetrical manner. Low back pain occurs in half the patients with reactive arthritis and heel pain is a common symptom due to inflammation of the Achilles insertion into the heel bone. The weight bearing joints are mostly affected but others can be, with hands and feet affected in more severe and long term cases. Whilst spinal involvement is common there are typically few examination findings apart from some loss of lumbar flexion.
Chronic and ongoing joint arthritis and poorly limited inflammatory reactions may mean a rheumatologist will prescribe drugs known as DMARDS or disease modifying anti-rheumatoid drugs. These have been tested on conditions such as rheumatoid arthritis or ankylosing spondylitis but their usefulness in reactive arthritis has not been shown. Typical examples are methotrexate and sulphasalazine. The newer biological drug treatments have been effective in some conditions but have not yet been shown to be useful in this condition.