Here at Boston Children's Hospital, we understand that juvenile arthritis is both easy and hard to define. The word “arthritis” literally means “joint inflammation” (arth=joint); itis=inflammation); “juvenile” describes a disease affecting children under the age of 16. So if your young child has inflammation—swelling, stiffness, warmth and redness—in his joints, you might say he has juvenile arthritis.
Yet it wouldn’t be the whole story: Juvenile arthritis isn’t one condition, but encompasses many dozens of conditions that affect different parts of the body, progress in different ways and often have very different treatments and outcomes. Symptoms may last only a short while, while others are chronic, meaning they last for months or years.
The doctors who specialize in diagnosing arthritis are called rheumatologists, and they’re the ones who will best identify what kind of arthritis your child has and explain how it should be treated. Among the illnesses they may discuss with you are the ones listed below.
Types of arthritis and other rheumatic diseases
Juvenile idiopathic arthritis (JIA)
For years, juvenile idiopathic arthritis was called juvenile rheumatoid arthritis, and you may still hear that term or its abbreviation, JRA. The name has recently changed, however, to emphasize differences between JIA and adult rheumatoid arthritis.
JIA is any arthritis with no known cause (this is what “idiopathic” means) whose symptoms last for at least six weeks in a child younger than 16. There are three main subtypes:
- oligoarticular, which involves four joints or fewer; also known as pauciarticular JIA
- polyarticular, which involves five or more joints
- systemic, which begins with fevers, rashes and inflammation in other parts of the body as well as the joints (“systemic” means a disease that affects the body as a whole); sometimes also called Still’s disease after the English physician who first described it, Sir George Frederic Still.
You may also encounter terms describing two other kinds of illnesses included under JIA:
- psoriatic arthritis, an inflammation of the joints that occurs in some children with the skin condition psoriasis
- enthesitis-related arthritis (ERA),an inflammation of the entheses, the places where tendons and ligaments attach to bones. This category of arthritis is sometimes called “spondyloarthritis,” and includes ankylosing spondylitis (which primarily affects the spine).
To learn more about a particular type of arthritis—including how it may affect your child’s health and what treatments Children’s offers—visit the links within the text on this page.
Also known as infectious arthritis, septic arthritis is distinct from JIA because it has a known cause: namely, a bacterial infection within the joint. Usually this happens when bacteria spread to the joint via the bloodstream, but joints also can become directly infected due to injury or surgery. Septic arthritis typically affects just one joint, and most children recover quickly if treated immediately with antibiotics.
Arthritis accompanying other illnesses
- Arthritis is often part of Lyme disease, an infection caused by a bacterium transmitted by deer ticks. Lyme arthritis most commonly affects the knee but occasionally appears in other joints. In most cases, Lyme arthritis can be easily diagnosed with a blood test, and it usually responds very well to antibiotics.
Because arthritis most often stems from immune system problems—in which the body’s natural defenses mistakenly attack healthy tissue—it’s also frequently part of other autoimmune diseases, such as:
Because juvenile arthritis comes in many different forms, it can be a mild illness or a very serious one. But in all cases doctors will focus on extinguishing the “fire” of inflammation, to give children’s joints and bones the possible best chance to develop normally.