Diagnosing juvenile idiopathic arthritis

Inflammatory arthritis in children and young people is a disease of unknown aetiology with a significant burden in terms of morbidity and disability. Prompt diagnosis is essential as effective treatments are available. The term juvenile idiopathic arthritis (JIA) has been widely adopted to describe this heterogeneous group of diseases, following the classification system published by the International League of Associations for Rheumatology (ILAR). This is an attempt to unite the historical gap between American and European terminology in which the terms juvenile rheumatoid arthritis and juvenile chronic arthritis, respectively, were used. Standardized diagnosis has improved comparability of research and in turn has enhanced the evidence base in JIA.The diagnosis of JIA is predominantly clinical and this review outlines the clinical features of the condition together with an approach to differential diagnosis. The role of the limited laboratory testing is reviewed, along with recent advances in imaging which can aid diagnosis. Of particular importance are joint ultrasound, which has the potential to be used routinely in the consulting room as part of a clinician’s assessment, and MRI that can provide early diagnostic clues to JIA.