What is juvenile idiopathic arthritis?

Juvenile idiopathic arthritis (JIA) is the most common type of arthritis that affects children. JIA is a chronic (long-lasting) disease that can affect joints in any part of the body.

JIA is an autoimmune disease in which the body’s immune system mistakenly targets the synovium, the tissue that lines the inside of the joint, and the synovial fluid in the joint. This causes the synovium to make extra synovial fluid, which leads to swelling, pain and stiffness in the joint.

This process can spread to the nearby tissues, eventually damaging cartilage and bone. Other areas of the body, especially the eyes, may also be affected by the inflammation. If it is not treated, JIA can interfere with a child’s normal growth and development.

What are the types of juvenile idiopathic arthritis?

There are several types of JIA, depending on the symptoms and the number of joints involved:

  • Oligoarthritis: This type of JIA affects fewer than five joints, most often in the knee, ankle and elbow. It also can cause uveitis, an inflammation of the middle layer of the eye (the uvea). Uveitis may be undetectable without a dedicated eye exam. About half of all children with JIA have oligoarthritis; it is more common in girls than in boys. Many children will outgrow oligoarthritis by adulthood. In some children, it may spread to eventually involve more joints.
  • Polyarthritis: This type of JIA affects five or more joints, often the same joints on each side of the body. Polyartritis can also affect the neck and jaw joints and the smaller joints, such as those in the hands and feet. It is more common in girls than in boys and accounts for 20 percent of JIA patients
  • Psoriatic arthritis: This type of arthritis affects children who have arthritis and psoriasis, a rash that causes raised red patches or skin lesions covered with a silvery white buildup of dead skin cells. Psoriatic arthritis can also cause nail changes that look like dimpling or pitting.
  • Enthesitis-related arthritis: Also known as spondyloarthropathy. This type of arthritis often affects the spine, hips and entheses (the points where tendons and ligaments attach to bones), and occurs mainly in boys older than seven years. The eyes are often affected in this type of arthritis, and may become painful or red.
  • Systemic arthritis: Also called Still's disease, this type occurs in about 10 to 20 percent of children with JIA. A systemic illness is one that can affect the entire body or many body systems. Besides arthritis, systemic JIA usually causes persistent high fever and rash, which most often appears on the trunk, arms and legs when fever spikes. It can also affect internal organs, such as the heart, liver, spleen and lymph nodes. This type of JIA affects boys and girls equally and rarely affects the eyes.

How common is juvenile idiopathic arthritis?

JIA is the most common type of arthritis in children. It affects about 1 in 1,000 children, or about 300,000 children in the United States.

What causes juvenile idiopathic arthritis?

The causes of JIA are not known. Factors that may be involved, alone or in combination, include genetics (the disease may be inherited), infection and environmental factors that influence the immune system.

What are the symptoms of juvenile idiopathic arthritis?

Symptoms vary depending on the type of JIA and may include:

  • Pain, swelling and tenderness in the joints. The joints may also feel warm.
  • Morning joint stiffness
  • Limping gait (younger children may not be able to perform motor activities that they recently learned)
  • Fever
  • Rash
  • Weight loss
  • Swollen lymph nodes
  • Fatigue or irritability
  • Eye redness, eye pain, and blurred vision

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