context: Reactive arthritis, formerly referred to as Reiter's syndrome, is a form of arthritis that affects the joints, eyes, urethra (the tube that carries urine from the bladder to the outside of the body), and skin. The disease is recognized by various symptoms in different organs of the body that may or may not appear at the same time. It may come on quickly and severely or more slowly, with sudden remissions or recurrences. Reactive arthritis primarily affects sexually active males between the ages of 20 and 40. Those with HIV (human immunodeficiency virus) are at a particularly high risk. The cause of reactive arthritis is still unknown, but research suggests the disease is caused, in part, by a genetic predisposition: Approximately 75% of those with the condition have a positive blood test for the genetic marker HLA- B27. In sexually active males, most cases of reactive arthritis follow infection with Chlamydia trachomatis or Ureaplasma urealyticum, both sexually transmitted diseases. In other cases, people develop the symptoms following an intestinal infection with shigella, salmonella, yersinia, or campylobacter bacteria. Besides using condoms during sexual activity, there is no known preventative measure for reactive arthritis. The first symptoms of reactive arthritis are painful urination and a discharge from the penis if there is inflammation of the urethra. Diarrhea may occur if the intestines are affected. This is then followed by arthritis four to 28 days later that usually affects the fingers, toes, ankles, hips, and knee joints. Typically, only one or a few of these joints may be affected at one time. Other symptoms include: Mouth ulcers Inflammation of the eye Keratoderma blennorrhagica (patches of scaly skin on the palms, soles, trunk, or scalp) Back pain from sacroiliac ( SI) joint involvement Pain from inflammation of the ligaments and tendons at the sites of their insertion into the bone (enthesitis) Diagnosis of reactive arthritis can be complicated by the fact that symptoms often occur several weeks apart. A doctor may diagnose reactive arthritis when the patient's arthritis occurs together with or shortly following inflammation of the eye and the urinary tract and lasts a month or longer. There is no specific test for diagnosing reactive arthritis, but the doctor may check the urethral discharge for sexually transmitted diseases. Stool samples may also be tested for signs of infection. Blood tests of reactive arthritis patients are typically positive for the HLA- B27 genetic marker, with an elevated white blood cell count and an increased erythrocyte sedimentation rate ( ESR) -- both signs of inflammation. The patient may also be mildly anemic (having too few red blood cells in the bloodstream). X-rays of the joints outside the back do not usually reveal any abnormalities unless the patient has had recurrent episodes of the disease. On an X-ray, joints that have been repeatedly inflamed may show areas of bone loss, signs of osteoporosis, or bony spurs. Joints in the back and pelvis (sacroiliac joints) may show abnormalities and damage from reactive arthritis. Bacterial infections, such as chlamydia, will need to be treated with antibiotics. Joint inflammation from reactive arthritis is usually treated with nonsteroidal anti-inflammatory drugs ( NSAIDs), such as naproxen, aspirin, or ibuprofen. Skin eruptions and eye inflammation can be treated with steroids. Those with chronic disease may be prescribed other medications, including methotrexate. Patients with chronic arthritis also may be referred to a physical therapist and may be advised to exercise regularly. The prognosis for reactive arthritis varies. Most people recover in three to four months, but about half have recurrences for several years. Some people develop complications that may include inflammation of the heart muscle, inflammation with stiffening of the spine, glaucoma, progressive blindness, feet abnormalities, or accumulation of fluid in the lungs.