Overview of JIA
Munro, 2014Onel, 2022Ringold, 2019
Juvenile idiopathic arthritis (JIA) (also known as juvenile arthritis, juvenile rheumatoid arthritis [JRA] or juvenile chronic arthritis [JCA]) describes any inflammatory arthritis with an onset before 16 years of age that persists for at least 6 weeks and for which no underlying cause can be found after appropriate investigation. It is the most common rheumatological disease in childhood, affecting approximately 1 in 1000 children.
JIA is a heterogeneous condition that encompasses multiple subtypes that vary in their pattern of joint involvement and extra-articular disease, clinical course, prognosis and pathophysiology. Subtypes of JIA includePetty, 2004:
- oligoarticular JIA—up to 4 joints involved in the first 6 months
- polyarticular JIA—more than 4 joints involved in the first 6 months. Can be either
- systemic JIA—can have oligo- or polyarticular arthritis, but may have preceding systemic features similar to the rarer adult-onset Still disease
- enthesitis-related arthritis (also know as juvenile spondyloarthritis)—can have peripheral (sacroiliac joint) and axial (spine) arthritis
- psoriatic JIA—can have oligo- or polyarticular arthritis, and may have associated psoriatic rash and nail pitting.
There is a broad spectrum of differential diagnoses of JIA, ranging from benign noninflammatory conditions such as irritable hip (transient synovitis) to malignancy. Before starting long-term therapy for JIA, thorough assessment by a paediatric rheumatologist with experience with the diagnosis and its differentials is recommended (see also Assessing musculoskeletal symptoms in children and adolescents).