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Oligoarticular,Polyarticular, and Systemic Categories: Introduction
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Arthritis is a clinical finding of persistent
joint swelling or painful restriction of joint movement. Arthralgia is
pain in a joint, with or without inflammation. Thus, a patient with
arthralgia will not necessarily have arthritis, nor does a patient
with arthritis always have arthralgia. There are many causes of
arthritis and arthralgia in childhood, and this section will be
limited to the chronic arthritides of childhood that have no known
cause.
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Terminology for this category of disease is problematic: In ongoing
attempts to rationalize the nomenclature, at least three different
classification schemes have been used during the past 20 years (see eTable 201.1). Without a clear-cut understanding
of the pathogenesis or biologic variability of arthritis in children,
however, these systems have often served more to confuse than to
elucidate. Idiopathic arthritis lasting for at least 6 weeks; with
onset before age 16; and not the result of infections, neoplasms,
orthopedic disorders, chronic inflammatory or autoimmune conditions,
or metabolic inherited and endocrine diseases, will be referred
to as juvenile idiopathic arthritis (JIA) in this section. This term
is increasingly used internationally to describe this group of conditions.
Details of the definitions and subcategories within this system are
shown in Table 201-1. The Juvenile Rheumatoid
Arthritis system still used by most caregivers in the United States
is shown in Table 201-2.
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