Novel insights into the biology of childhood arthritis- lessons learned from the synovium

Chronic inflammatory arthritis of childhood, known as juvenile idiopathic arthritis (JIA), exhibits distinct and shared features with adult-onset disease. Recent advances in minimally invasive synovial biopsy, high resolution imaging and sequencing technologies have enabled detailed characterisation of the inflamed synovium in JIA, facilitating insights into the underlying immunopathology. In this review we draw on these findings to consider how the developing immunological and structural context of the joint impacts the presentation and consequence of inflammatory joint disease in children and young adults.