Inflammation in juvenile idiopathic arthritis

The pediatric arthritides encompass the seven types of juvenile idiopathic arthritis (JIA) (formerly known as juvenile rheumatoid arthritis and juvenile chronic arthritis) as well as granulomatous arthritis caused by pediatric sarcoid, or by Blau syndrome. Many of the recent studies on pathogenesis have simply divided patients into three categories: oligoarthritis, polyarthritis, and systemic arthritis. Where the existing data allow, this article uses the approved Durban criteria (Box 1) [1]. In many cases, however, the older data do not reflect the more recent understanding of the clinical subsets. Pediatric arthritides are both similar and distinct from adult-onset arthritides. For example, spondyloarthropathies and rheumatoid arthritis may present in childhood. The course of rheumatoid factor-positive JIA proceeds in childhood in a manner similar to rheumatoid arthritis seen in adults [2], whereas the spondyloarthropathies have a course that is marked by increased extra-axial symptoms and modest sacroiliitis compared with adults [3]. The other types of JIA are unique to children. Recent studies have begun to expose the distinct types of inflammation occurring in these disorders.