Classifications and imaging of juvenile spondyloarthritis.

Juvenile spondyloarthritis may be present in at least 3 subtypes of juvenile idiopathic arthritis according to the classification of the International League of Associations for Rheumatology. By contrast with spondyloarthritis in adults, juvenile spondyloarthritis starts with inflammation of peripheral joints and entheses in the majority of children, whereas sacroiliitis and spondylitis may develop many years after the disease onset. Peripheral joint involvement makes it difficult to differentiate juvenile spondyloarthritis from other juvenile idiopathic arthritis subtypes. Sacroiliitis, and especially spondylitis, although infrequent in childhood, may manifest as low back pain. In clinical practice, radiographs of the sacroiliac joints or pelvis are performed in most of the cases even though magnetic resonance imaging offers more accurate diagnosis of sacroiliitis. Neither disease classification criteria nor imaging recommendations have taken this advantage into account in patients with juvenile spondyloarthritis. The use of magnetic resonance imaging in evaluation of children and adolescents with a clinical suspicion of sacroiliitis would improve early diagnosis, identification of inflammatory changes and treatment. In this paper, we present the imaging features of juvenile spondyloarthritis in juvenile ankylosing spondylitis, juvenile psoriatic arthritis, reactive arthritis with spondyloarthritis, and juvenile arthropathies associated with inflammatory bowel disease.