Is it time for the International League of Associations for Rheumatology juvenile idiopathic arthritis ‘class’ification to graduate?

Under the organization of the International League of Associations for Rheumatology (ILAR), the widely applied current classification system for juvenile idiopathic arthritis (JIA) was established in 1995 [1] and revised in 1997 [2] and 2001 [3]. The main goal of this new classification of childhood arthritides was to develop criteria that would identify homogeneous groups of children with chronic arthritis to facilitate research in immunogenetics, epidemiology, outcomes and therapy. There are seven categories in this schema: systemic arthritis; oligoarthritis, persistent or extended; polyarthritis rheumatoid factor (RF); polyarthritis RF; psoriatic arthritis; enthesitis-related arthritis (ERA); and undifferentiated arthritis. Although the ILAR classification has performed relatively well compared with previous classifications of JIA, the exclusion criteria designed to keep each category pristine, have been controversial and for some subgroups appear to be too rigid. As a result, many patients with other wise homogeneous features are assigned to the ‘undifferentiated arthritis’ set, which becomes a mixture of chronic arthritides that lack inclusion criteria for other categories. This subset, by virtue if it’s lack of homogeneity, is least likely to lend itself to research and therapeutic scrutiny. Burgos-Vargas et al. [4] and Colbert [5] have pointed out in detail that the criteria for ERA are skewed toward the undifferentiated forms of spondyloarthritis, which are common presenting features of anklylosing spondylitis (AS) in childhood and away from those forms presenting with early axial disease or coexisting conditions, such as inflammatory bowel disease. By contrast, the European Spondyloarthritis Study Group [6] and the criteria of Amor et al. [7], which are used in adults with no lower age limit, are more inclusive of these common features. With regards to the ILAR ERA subgroup, only 56.7% of the