Overview of Reactive Arthritis 

Reactive arthritis, as the name suggests, occurs in reaction to something—in this case, an infection. The condition is triggered by a bacterial infection in the digestive or urinary tract or the genitals, but arthritis symptoms typically do not set in until after you have recovered from the infection. Inflammation of the joints, eyes, and urinary tract are hallmarks of reactive arthritis, but not everyone gets all three, or they might not occur at the same time.

The knee and ankle joints are frequently affected, and many people experience pain in the sacroiliac joints in the lower back as well. Reactive arthritis is a form of spondyloarthritis, a group of arthritis conditions that typically involve the sacroiliac joints in the lower back, and entheses (places where tendons or ligaments attach to bones). Foot pain in people with reactive arthritis is usually due to inflammation of entheses.

The symptoms often clear up on their own within a few weeks or months, but they may become chronic (long-lasting) in some people. Doctors tailor treatment to each individual’s symptoms, and therapy typically involves a combination of medications and exercise.

Who Gets Reactive Arthritis?

Anyone can get reactive arthritis, and it occurs worldwide. A bacterial infection—in the digestive or urinary tract or the genitals—typically precedes it by a few weeks. Although sexually transmitted infections can occur just before the onset of reactive arthritis, many cases of reactive arthritis are associated with other types of infections that are not transmitted sexually. Certain factors increase the risk of the condition, including:

  • Sex. Both men and women can get reactive arthritis, but men are more likely to develop it as a result of a sexually transmitted infection. Men and women are equally affected if the condition is from a gastrointestinal infection.
  • Age. It occurs most often in people between ages 20 and 40.
  • Genetics. People who have a gene called HLA-B27 have a higher risk of getting reactive arthritis and of experiencing more severe and more long-lasting symptoms. But people who lack HLA-B27 can still get the condition.
  • HIV infection. Having AIDS or being infected with HIV increases the risk of reactive arthritis.

Symptoms of Reactive Arthritis

Some people with reactive arthritis have mild symptoms, while others have severe symptoms that limit daily activities. The symptoms typically start 1 to 6 weeks after an infection of the digestive or urinary tract or genitals, but the infection has usually resolved by the time symptoms arise. The onset is typically fairly sudden, usually over the course of a few days.

Reactive arthritis is characterized by inflammation of the joints, eyes, and urinary tract, but not everyone with the condition will experience all three, or they might not occur at the same time. The main symptoms are:

  • Joint pain and stiffness.
    • Joints may become painful, red, and swollen, especially the large joints of the lower limbs, such as the knees and ankles. Morning stiffness or nighttime pain is typical. The affected joints are usually on one side of the body. There may be pain in the lower back and buttocks as well.
    • Pain in the heel or foot pain is a sign of enthesitis (inflammation at a place where a tendon or ligament attaches to a bone).
    • Swollen, inflamed, painful fingers or toes (dactylitis) may also occur.
  • Inflammation of the urinary tract.
    • This symptom is more common when reactive arthritis happens after an infection of the genitals or urinary tract.
    • In women, urinary tract inflammation can develop into inflammation of the cervix, fallopian tubes, vulva, or vagina.
    • Increased urinary frequency and burning while urinating are signs of urinary tract inflammation. 
  • Eye inflammation.
    • Conjunctivitis (inflammation of the transparent layer that covers the white part of the eye and lines the eyelids) and uveitis (inflammation of the middle part of the eye) can cause redness, pain, burning, itching, crusted eyelids, blurred vision, or sensitivity to light.

Other symptoms of reactive arthritis include:

  • Fatigue or feeling generally unwell.
  • Fever.
  • Weight loss.
  • Diarrhea and abdominal pain.
  • Small ulcers in the mouth.
  • In men, small, painless ulcers on the penis.
  • Skin rash (keratoderma blennorrhagica) consisting of reddish, raised bumps, usually on the palms or soles. The bumps may merge, forming a larger scaly rash.
  • Thickened nails.

The symptoms of reactive arthritis often clear up on their own within a few weeks or months, but they may become chronic (long-lasting) in some people.

Causes of Reactive Arthritis

Reactive arthritis is triggered by an infection—frequently a sexually transmitted or food-borne bacterial infection—but it is separate from the infection and typically sets in after the infection has cleared. The bacteria that commonly trigger it are Salmonella, Yersinia, Campylobacter, Shigella, and Chlamydia, but only a minority of people infected with them develop the condition. Scientists do not fully understand why some people are predisposed to getting reactive arthritis.

Genetics seems to partly explain susceptibility to the condition, as many affected individuals have a gene called HLA-B27. However, many people who get reactive arthritis lack this genetic marker so there are other, as yet unknown, genetic and environmental contributing factors.

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