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INTRODUCTION

ESSENTIALS OF DIAGNOSIS

  • Juvenile idiopathic arthritis (JIA) is a heterogeneous group of diseases which describe chronic inflammatory arthritis in a child lasting longer than 6 weeks with onset prior to 16 years of age.

  • Disease subtypes vary with respect to clinical presentation, extra-articular symptoms, and serology.

  • There is no specific laboratory test or imaging modality that can confirm or exclude a diagnosis of JIA.

  • Complications of JIA include uveitis, macrophage activation syndrome (MAS), contractures, and growth abnormalities.

  • Treatment varies with respect to subtype classification.

General Considerations

Juvenile idiopathic arthritis (JIA) refers to a heterogeneous group of diseases, all of which describe chronic inflammatory arthritis lasting longer than 6 weeks with onset prior to 16 years of age. There are three major classification systems: the American College of Rheumatology (ACR), the European League Against Rheumatism (EULAR), and the International League of Associations for Rheumatology (ILAR) (Table 18–1). The ILAR criteria serve to unify the discrepancies between the ACR and EULAR classification criteria and are more widely used in both the clinical setting and research studies. Prior to adaptation of the ILAR criteria, the terms juvenile rheumatoid arthritis (JRA) and juvenile chronic arthritis (JCA) were used interchangeably per ACR and EULAR criteria, respectively. JRA is a misnomer, as only a small percentage (3–5%) of children predominantly share features of adult rheumatoid arthritis (RA) (Berntson et al, 2001; Brewer et al, 1977; Petty et al, 2001).

Table 18–1.Historical classification of juvenile arthritis.

In accordance with ILAR classification, JIA is further divided into seven distinct subtypes: oligoarticular, rheumatoid factor (RF)–positive polyarticular, RF-negative polyarticular, systemic, psoriatic, enthesitis-related, and undifferentiated. These subtypes vary with respect to clinical presentation, disease course, and pathophysiology, and subsequently respond differently to treatments currently available. Classification is based on the number of arthritic joints, RF and human leukocyte antigen-B27 (HLA-B27) positivity, medical history, and associated extra-articular manifestations (Table 18–2) (Petty et al, 2001).

Table 18–2.International League of Associations for Rheumatology (ILAR) classification.

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