Juvenile Idiopathic Arthritis

Abstract

The term juvenile idiopathic arthritis (JIA) encompasses a heterogeneous group of chronic arthritides that share the following features: (1) disease onset before 16 years of age and (2) a minimum duration of 6 weeks. For many years, it was named juvenile rheumatoid arthritis (mainly in the American literature) and chronic juvenile arthritis (mostly in European texts). It is an autoimmune inflammatory disease of unknown etiology that occurs most often in females, whose main target tissue is the synovium. Synovitis is present since the very early stages of JIA, with gradual development of synovial hyperplasia and hypercellular pannus, which eventually erodes cartilage and bone. Even though this diagnosis is essentially a clinical one, recent therapeutic advances have drastically changed the role of imaging in its management. Children with JIA must be diagnosed as soon as possible, aiming at a benign course and a better outcome with timely introduction of treatment. Magnetic resonance imaging is especially useful as it allows for early demonstration of abnormal findings, monitoring of disease progression, and accurate assessment of treatment response.