Whole-body MRI of juvenile spondyloarthritis: protocols and pictorial review of characteristic patterns.

Spondyloarthritides are a group of inflammatory rheumatological diseases that cause arthritis with a predilection for spinal or sacroiliac involvement in addition to a high association with HLA-B27. Juvenile spondyloarthritis is distinct from adult spondyloarthritis and manifests more frequently as peripheral arthritis and enthesitis. Consequently juvenile spondyloarthritis is often referred to as enthesitis-related arthritis (ERA) subtype under the juvenile idiopathic arthritis (JIA) classification criteria. The American College of Rheumatology Treatment Recommendations for JIA, including ERA, are based on the following clinical parameters: current treatment, disease activity and the presence of poor prognostic features. The MRI features of juvenile spondyloarthritis include marrow edema, peri-enthesal soft-tissue swelling and edema, synovitis and joint or bursal fluid. Marrow edema is nonspecific and can be seen with other pathologies as well as in healthy subjects, and this is an important pitfall to consider. With further longitudinal study and validation, however, whole-body MRI with dedicated images of the more commonly affected areas such as the spine, sacroiliac joints, hips, knees, ankles and feet can serve as a more objective tool compared to clinical exam for early detection and monitoring of disease activity and ultimately direct therapeutic management.