Reactive arthritis

Reactive arthritis is a condition that causes joint pain and swelling, also called inflammation, after an infection in another part of the body. The infection typically starts in the gut, genitals or urinary tract.

This condition typically affects the knees, ankles and feet. It also can cause inflammation in the eyes, the skin and the tube that carries urine out of the body, called the urethra. In the past, reactive arthritis was sometimes called Reiter syndrome.

Reactive arthritis is generally regarded as a form of spondyloarthritis (SpA). SpA is a group of inflammatory diseases that mainly affect the spine, joints, and places where tendons and ligaments attach to bones. The word comes from spondylo, meaning spine, and arthritis, meaning joint inflammation. SpA also is called enthesitis. These conditions share similar symptoms and genetic links, especially a gene called HLA-B27.

Reactive arthritis isn't common and typically happens for a limited time. For most people, symptoms come and go and usually disappear within a year.

The symptoms of reactive arthritis typically start 1 to 4 weeks after you've had a triggering infection. Common symptoms include:

• Pain and stiffness. This often affects the knees, ankles and feet. You may also feel pain in your heels, lower back or buttocks.
• Eye inflammation. Many people with reactive arthritis also develop red, irritated or painful eyes. These symptoms may be signs of conjunctivitis, commonly known as pink eye. Blurred vision also may be a symptom.
• Urinary issues. You may need to urinate more often. You may feel burning or discomfort when you do. In some people, there may be inflammation of the prostate gland or the cervix.
• Inflammation of tendons and ligaments where they attach to bone, called enthesitis. This happens most often in the heels and the soles of the feet.
• Swollen toes or fingers. They may become so swollen that they look like sausages.
• Skin issues. Some people get mouth sores, painless ulcers on the penis, or a rash on the palms of the hands or soles of the feet.
• Low back pain. The pain tends to be worse at night or in the morning.

Reactive arthritis happens when the immune system reacts to an infection somewhere else in the body — usually in the intestines, genitals or urinary tract. Sometimes the infection is so mild that you may not even know you had it.

Reactive arthritis itself is not contagious, but the bacteria that cause it can spread through sex or food. Several types of bacteria can trigger reactive arthritis. Common examples include:

• Chlamydia trachomatis. It is spread through sexual contact. The infection typically starts in the urethra, bladder or vagina.
• Clostridium difficile (C. difficile), Escherichia coli (E. coli), campylobacter, salmonella, shigella and yersinia. These bacteria typically infect the gastrointestinal tract, causing diarrhea or other stomach and intestinal symptoms.

Only a small number of people who are exposed to these bacteria develop reactive arthritis.

Certain factors increase the risk of reactive arthritis:

• Age. It most often affects adults between 20 and 40 years old.
• Sex assigned at birth. People are equally likely to get reactive arthritis from foodborne infections. But people assigned male at birth are more likely to develop it after a sexually transmitted infection.
• Genetics. Having a certain genetic marker (HLA-B27) increases the risk. But most people with this marker never get reactive arthritis.
• Infection. Having HIV increases the risk of developing reactive arthritis.

You can't change your genes, but you can lower your risk of reactive arthritis by reducing exposure to bacteria that cause infections.

• Practice food safety. Keep food at the right temperature and cook it thoroughly to avoid bacteria that can cause reactive arthritis.
• Prevent sexually transmitted infections. Use condoms to help protect you from bacteria such as chlamydia that may trigger reactive arthritis.