juvenile idiopathic arthritis










The incidence of juvenile idiopathic arthritis in North America and Europe is estimated to be 4 to 16 in 10,000 children. One in 1,000, or approximately 294,000, children in the United States are affected. The most common type of juvenile idiopathic arthritis in the United States is oligoarticular juvenile idiopathic arthritis, which accounts for about half of all cases. For reasons that are unclear, females seem to be affected with juvenile idiopathic arthritis somewhat more frequently than males. However, in enthesitis-related juvenile idiopathic arthritis males are affected more often than females. The incidence of juvenile idiopathic arthritis varies across different populations and ethnic groups.

Juvenile idiopathic arthritis is thought to arise from a combination of genetic and environmental factors. The term "idiopathic" indicates that the specific cause of the disorder is unknown. Its signs and symptoms result from excessive inflammation in and around the joints. Inflammation occurs when the immune system sends signaling molecules and white blood cells to a site of injury or disease to fight microbial invaders and facilitate tissue repair. Normally, the body stops the inflammatory response after healing is complete to prevent damage to its own cells and tissues. In people with juvenile idiopathic arthritis, the inflammatory response is prolonged, particularly during movement of the joints. The reasons for this excessive inflammatory response are unclear.

Researchers have identified changes in several genes that may influence the risk of developing juvenile idiopathic arthritis. Many of these genes belong to a family of genes that provide instructions for making a group of related proteins called the human leukocyte antigen (HLA) complex. The HLA complex helps the immune system distinguish the body's own proteins from proteins made by foreign invaders (such as viruses and bacteria). Each HLA gene has many different normal variations, allowing each person's immune system to react to a wide range of foreign proteins. Certain normal variations of several HLA genes seem to affect the risk of developing juvenile idiopathic arthritis, and the specific type of the condition that a person may have.

Normal variations in several other genes have also been associated with juvenile idiopathic arthritis. Many of these genes are thought to play roles in immune system function. Additional unknown genetic influences and environmental factors, such as infection and other issues that affect immune health, are also likely to influence a person's chances of developing this complex disorder.

Most cases of juvenile idiopathic arthritis are sporadic, which means they occur in people with no history of the disorder in their family. A small percentage of cases of juvenile idiopathic arthritis have been reported to run in families, although the inheritance pattern of the condition is unclear. A sibling of a person with juvenile idiopathic arthritis has an estimated risk of developing the condition that is about 12 times that of the general population.

  • arthritis, juvenile rheumatoid
  • JIA
  • JRA
  • juvenile chronic arthritis
  • juvenile RA
  • juvenile rheumatoid arthritis
  • systemic juvenile rheumatoid arthritis