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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 children, and this section will be limited to the chronic arthritides of childhood that have no known cause.

The heterogeneous nature of childhood arthritis continues to impose challenges as to the most descriptive terminology. At least 3 different classification schemes have been developed: juvenile rheumatoid arthritis (JRA) by the American College of Rheumatology (ACR), juvenile chronic arthritis (JCA) by the European League of Rheumatology (EULAR), and juvenile idiopathic arthritis (JIA) by the International League of Associations for Rheumatology (ILAR) (Table 198-1). These classifications share some common features: disease onset before age 16 years; minimum period of duration of arthritis (6 weeks for ACR and ILAR and 6 months for EULAR); and use of terms to describe the pattern of disease during the first 6 months from onset, with oligoarticular (or pauciarticular) arthritis occurring in 4 or fewer joints and polyarticular arthritis occurring in 5 or more joints. Systemic in all schemes refers to arthritis in association with characteristic fever and other extra-articular features, including rash, lymphadenopathy, hepatosplenomegaly, or serositis. The presence of rheumatoid factor has also been recognized as a defining feature for subclassification, and in the EULAR system, patients with rheumatoid factor are classified as having JRA, whereas in the ILAR system, these patients are classified as having rheumatoid factor–positive polyarthritis.

A major deficiency of the ACR, EULAR, and current ILAR classification systems is in how they deal with childhood spondyloarthropathies. They are respectively not included, incompletely included, or inadequately described in the context of adult disease. These deficiencies are further discussed in the section on enthesitis-related arthritis and the spondyloarthropathies (see Chapter 199).

The ILAR classification system has gained a great deal of international acceptance to replace the 2 previous parallel systems, and although at times it is complicated to use and is decidedly imperfect, it has been the preferred system for most of the world, giving it a cache lacking in the previous systems. As studies have enrolled patients according to the ILAR criteria, the transition in nomenclature has been made, and it is hoped that the next modification in terminology will be based firmly on genetic and pathogenic data.

Clinicians, however, need to be reminded that there is a wealth of literature on JRA and JCA that cannot be ignored and that must be applied to patients within the new ILAR classifications.

Juvenile arthritis lasting for at least 6 weeks, with onset before age 16, and not the result of infections, neoplasms, orthopedic disorders, other chronic inflammatory or autoimmune conditions, or metabolic inherited and endocrine diseases, will ...

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