Reactive arthritis is a condition in which there is inflammation of the joints with pain and swelling which occurs following an infection elsewhere in the body. The joint itself is not infected and often the primary infection has already resolved. This is a rare conditions occurring in about 0.6 to 27 people per 100,000 population, affecting predominantly young adults with equal incidence in men and women.
Cause of Reactive Arthritis
This is believed to occur as a systemic inflammatory response to the initial infection. The preceding infection is usually in the gut or from the urinary tract. The following organisms are frequently implicated:
Symptoms of Reactive Arthritis
The person typically experiences symptoms of reactive arthritis 1 to 4 weeks after the inciting infection which is usually diarrhea or a urinary tract infection. The following are the symptoms experienced:
- Joint pain: this is generally experienced in fewer than 2 to 3 joints. The knee is most commonly affected. Small joint of the hand may also be affected. The pain is sudden in onset.
- Joint swelling and redness: this is seen in a similar pattern to that described above
- Inflammation of soft tissue around joints: this is termed enteritis and is manifested most commonly as heel pain and swelling from inflammation around the Achilles tendon insertion into the heel.
- Lower back pain
Symptoms involving sites other than the musculoskeletal system
- Inflammation of the eye: this may be in the form of conjunctivitis (involving the outer lining of the eye), uveitis (involving the inner layers of the eye), keratitis (involving the cornea). They generally present as a red painful eye which may be associated with vision abnormalities
- Urinary tract inflammation with pain on passing urine: this can occur even when the inciting infection is in the gut. The urine culture in the setting would generally be sterile
Diagnosis of Reactive Arthritis
The clinical features of joint involvement along with a history of prior infection in the gut or the urinary tract suggests the diagnosis. The following lab tests are done to confirm the diagnosis of reactive arthritis:
- Stool culture, urinary or genital swab: these tests are done to confirm the presence of a prior or current infection.
- Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP): These are inflammatory markers and are elevated in reactive arthritis.
- Synovial fluid analysis: this is the process of obtaining and examining the fluid present in the joints. The test is performed by aspirating the joint fluid through a needle.
- Genetic testing for HLA-B27: An increased level of HLA-B27 is a risk factor for developing reactive arthritis along with many other inflammatory joint conditions. Individuals with elevated levels are prone to develop chronic reactive arthritis.
- Imaging: X rays and MRIs may be done but are generally non-specific.
Tests to rule out other causes of arthritis need to be done including testing for rheumatoid arthritis, systemic lupus erythematosus (SLE), Lyme arthritis and septic arthritis.
Treatment of Reactive Arthritis
- Treatment of the underlying infection: In the event of ongoing infection, antibiotics should be prescribed to control it.
- Non-steroidal anti-inflammatory drugs (NSAIDs): These are the first-line medicines given for pain relief and to control inflammation.
- Intra-articular glucocorticoids: This is a local injection of steroids into the joint space itself to reduce infection in the joint while avoiding systemic side effects.
- Oral steroids: Prednisone may be given orally if NSAIDs and intra-articular treatment have been unsuccessful
- Steroid sparing anti-inflammatory medications: these are medicines like methotrexate and sulfasalazine which are given in the case of reactive arthritis that has been unresponsive to previous treatments or if it has progressed to a chronic arthritis.
Prognosis of Reactive Arthritis
Generally, the symptoms resolve within 3 to 5 months. In most the symptoms decrease significantly by 6 to 12 months after the initial illness. However, a few individuals continue to have symptoms beyond this time and progress to chronic reactive arthritis requiring long-term therapy.