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:''This article does not deal with the more general topic of childhood arthritis.'' Juvenile idiopathic arthritis (JIA), also known as juvenile rheumatoid arthritis (JRA), is the most common form of arthritis in children and adolescents. (''Juvenile'' in this context refers to an onset before age 16,〔(【引用サイトリンク】title=Juvenile Idiopathic Arthritis (JIA): Joint Disorders: Merck Manual Professional )〕 ''idiopathic'' refers to a condition with no defined cause, and ''arthritis'' is the inflammation of the synovium of a joint.) JIA is an autoimmune, non-infective, inflammatory joint disease of more than 6 weeks duration in children less than 16 years of age. The disease commonly occurs in children from the ages of 7 to 12, but it may occur in adolescents as old as 15 years of age, as well as in infants. It is a subset of arthritis seen in childhood, which may be transient and self-limited or chronic. It differs significantly from arthritis commonly seen in adults (osteoarthritis, rheumatoid arthritis), and other types of arthritis that can present in childhood which are chronic conditions (e.g. psoriatic arthritis and ankylosing spondylitis). Aetiopathology is similar to rheumatoid arthritis but with less marked cartilage erosion, and joint instability and absent rheumatoid factor. JIA affects approximately 1 in 1,000 children in any given year, with about 1 in 10,000 having a more severe form. ==Terminology== The terminology used is evolving, and each term has some limitations. According to some sources, JIA replaces the term ''juvenile rheumatoid arthritis (JRA)''. Other sources still use the latter term. JIA is sometimes referred to as ''juvenile chronic arthritis (JCA)'',〔Dana D, Erstad S. Juvenile Idiopathic Arthritis. bchealthguide.org. Available at: (http://www.bchealthguide.org/kbase/topic/major/hw104391/descrip.htm ). Accessed on: March 11, 2007.〕 a term that is not precise as JIA does not encompass all forms of chronic childhood arthritis. A majority of cases are rheumatoid factor negative, which leads some to consider the "chronic" or "idiopathic" labels more appropriate.〔(【引用サイトリンク】title=Case Based Pediatrics Chapter )〕 However, if a cause was determined, then "idiopathic" may no longer be appropriate (making JIA a diagnosis of exclusion), and if the course was self-limited, then "chronic" may no longer be appropriate. Adding to the confusion, the term rheumatoid itself lacks a consistent, unambiguous definition. MeSH uses "Juvenile Rheumatoid Arthritis" as the primary entry, and uses "chronic" and "idiopathic" in alternate entries. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「juvenile idiopathic arthritis」の詳細全文を読む スポンサード リンク
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