Juvenile Idiopathic Arthritis
المؤلف:
Mary Louise Turgeon
المصدر:
Immunology & Serology in Laboratory Medicine
الجزء والصفحة:
5th E, P429-430
2025-10-05
117
Etiology
The term juvenile rheumatoid arthritis (JRA) has fallen out of favor worldwide for a number of reasons. JRA is not, as the language implies, simply a pediatric replica of the condition that affects adults. Only about 10% of children have an arthritic disease that closely mirrors rheumatoid arthritis in adults. Researchers have concluded that the JRA category is drawn too narrowly and should include some related diagnoses, such as ankylosing spondylitis. Juvenile idiopathic arthritis (JIA) and juvenile rheumatoid arthritis (JRA) can’t be used interchangeably because there are differences between the diagnoses they include (Table 1).
Table1. Subgroups of Juvenile Idiopathic Arthritis
Juvenile idiopathic arthritis (JIA) is a condition of chronic synovitis beginning during childhood. It is believed that there are a number of causes, including factors such as infection, autoimmunity, and trauma. Research at Tulane University Medical Center have suggested that JIA may be associated with a retroviral particle called human intracisternal A-type particle (HIAP). Antibodies to this particle have been found in a very high percentage of patients with JIA. These antibodies have also been found in many patients with three other auto immune disorders—SLE, Sjögren’s syndrome, and Graves’ dis ease. Researchers believe that these four disorders may result from the presence of HIAP, together with genetic factors and some internal or external stimulus, which all combine to dictate the specific symptomatology.
Epidemiology
The incidence of JIA in the U.S. pediatric population is from 0.1 to 1.1/1000.
Signs and Symptoms
Diagnostic criteria include onset before age 16 years, presence of arthritis (i.e., joint swelling for 6 consecutive weeks or longer), and exclusion of other conditions known to cause or mimic childhood arthritis. Several distinct subgroups of JIA have been recognized.
Immunologic Manifestations
Immunologic features of JIA can include the presence of RF, immune complexes, and ANAs.
Rheumatoid Factors
Approximately 20% of children are positive for RF. Most patients who are positive for RF probably represent adult RA occurring in childhood. So-called hidden RF can be detected in 65% of children with negative latex fixation test results. Children in this category do not develop the clinical manifestations of adults with RA.
Immune Complexes
Soluble immune complexes may be detected in patients with active synovitis. Analysis of these complexes is not useful for the diagnosis, prognosis, or monitoring of patients.
Antinuclear Antibodies
ANAs are detectable in few patients with JIA, except that most girls with pauciarthritis and chronic iritis demonstrate a positive ANA test result.
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