ABSTRACT
In 1977, members of the American College of Rheumatology (ACR) and the European League Against Rheumatism (EULAR) independently defined the terms juvenile rheumatoid arthritis (JRA) and juvenile chronic arthritis (JCA) respectively, to describe a clinically heterogeneous group of idiopathic arthritides occurring in children under the age of 16. Although these terms are often used interchangeably, they do not describe identical spectra of disease, leading to much confusion. Both groups of disorders have an age at onset before 16 years, and are subtyped according to the mode of onset: pauciarticular (four joints or less), polyarticular (more than four joints) and systemic (with other features of systemic disease such as fever, hepatosplenomegaly, lymphadenopathy or rash), after the exclusion of other causes. Whereas the EULAR criteria define JCA by degree of joint involvement after a minimal duration of 3 months, the ACR criteria define JRA at 6 weeks. Other differences occur in the exclusion of the spondyloarthropathies (juvenile ankylosing spondylitis, juvenile psoriatic arthritis, Reiter’s syndrome or arthropathies of inflammatory bowel disease) from the ACR classification of JRA, and the presence of rheumatoid factor (RF), which alters the EULAR criteria by replacing the term JCA with JRA. In an effort to unify the language, the International League of Associations of Rheumatologists (ILAR) has proposed a new set of classification criteria of juvenile idiopathic arthritis (JIA), the term intended to replace both JCA and JRA. Seven potential groups have been identified: systemic, oligoarthritis (four joints or less), polyarthritis (more than four joints) RF negative, polyarthritis RF positive, psoriatic arthritis, enthesitis-related arthritis, and other arthritides which fall outside, or fit more than one of the six main categories. The oligoarthritis group is further subcategorized into persistent (affecting no more than four joints throughout the disease course) or extended (affecting a cumulative total of five joints or more after the 6 months of disease). All have an age of onset before the sixteenth birthday and are characterized predominantly by an idiopathic arthritis, defined as arthritis persistent for at least 6 weeks, in which there is no defined diagnosis such as sepsis or rheumatic fever, and classification is made on the basis of listed criteria 6 months after disease onset.
