July 27, 2016
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Juvenile Idiopathic Arthritis (JIA, Arthritis in Childhood, Juvenile Rheumatoid Arthritis, JRA, Juvenile Chronic Arthritis)

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Juvenile idiopathic arthritis (JIA)/juvenile rheumatoid arthritis (JRA) facts

  • JIA was known in the U.S. as JRA (juvenile rheumatoid arthritis or juvenile RA).
  • Epidemiologic studies estimate that approximately 294,000 American children are affected by JIA.
  • Children of European ancestry are more likely to develop the condition while those of Japanese and Filipino background are less likely.
  • When considering the manifestation options of JIA, those children with European background are more likely to experience the oligoarticular version of JIA (see below) while those of African-American heritage are more likely have the rheumatoid factor (RF) positive, polyarticular juvenile idiopathic arthritis version (see below).
  • Among Caucasian children developing oligoarticular JIA, younger girls (2-4 years of age) are the most commonly affected.
  • The various epidemiologic patterns provide strong evidence of genetic influences for both the development of JIA as well as the clinical manifestations that may affect a child.

What is juvenile idiopathic arthritis (JIA)/juvenile rheumatoid arthritis (JRA)?

Juvenile idiopathic arthritis (JIA) is the umbrella term under which several forms of chronic arthritis in children are categorized. Regardless of type, all of these conditions have several historical and/or clinical characteristics in common. One or more joints must demonstrate evidence of inflammation characterized by swollen joints, limitation in the range of motion of the involved joint(s), tenderness when the joint is moved, and increased warmth of the joint region. These symptoms must be present (even intermittently) for at least six weeks and affect a child less than 16 years of age.

JIA is the most frequent chronic rheumatologic disease of childhood, and the cause(s) are not well understood. Both environmental and genetic influences are felt to contribute to the development of signs and symptoms of JIA. Knowledgeable specialists (pediatric rheumatologists usually affiliated with pediatric teaching hospitals) can help to limit the possibility of complications of juvenile idiopathic arthritis including leg-length discrepancy, joint contractures, and destruction and blindness due to inflammation of the eye (iritis).

Until the late 1990s, JIA was known in the U.S. as JRA (juvenile rheumatoid arthritis) and JCA (juvenile chronic arthritis) in Europe. The revised name was devised in order to better distinguish the childhood disease from rheumatoid arthritis (RA) that affects adults. This new nomenclature has enabled the categorization of six JIA subtypes. This updated classification has helped to foster better communication among those doing research on causation, clinical manifestations, and therapy of JIA.

JIA is considered a diagnosis of exclusion; the diagnosis can only be confidently made when (1) the patient's history, physical exam, and laboratory findings are consistent with those described in the literature by the International League of Associations for Rheumatology and (2) other conditions have been excluded. These include infection, malignancy, trauma, reactive arthritis, immunodeficiency, and connective tissue/rheumatologic diseases (for example, systemic lupus erythematosus).

What are causes and risk factors of juvenile idiopathic arthritis (JIA)/juvenile rheumatoid arthritis (JRA) arthritis?

While no specific cause(s) of JIA have been determined, there is strong evidence of both genetic and environmental factors being implicated in the development of the disease. Studies of the frequency of JIA have shown that if one identical twin develops the disease that the likelihood of their identical sibling developing JIA is 25%-40%. Studies of nonidentical siblings show evidence that if one child develops JIA there is a 15 to 30 times increased risk that a sibling will develop the condition when compared to the general pediatric population.

The biologic and clinical manifestations of JIA provide strong evidence that a general theme of an immune system misdirection is evident. The immune system has two "arms" -- the cell based (lymphocytes, etc.) and humeral based (antibodies). Rheumatologists have demonstrated that both of these elements of the immune system react against the patient's own body structures (joints, muscles, eye tissues, etc.). Much research is currently focused in an effort to better understand this autoinflammatory process in the hope that understanding the cause of JIA will enable better and more effective treatments and ultimately a cure for the condition.

Medically Reviewed by a Doctor on 8/4/2015

Source: MedicineNet.com


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