Spondyloarthritis SpA encompasses a broad spectrum of conditions occurring from childhood to middle age. Key features of SpA include axial and peripheral arthritis, enthesitis, extra-articular manifestations, and a strong association with HLA-B These features are common across the ages but there are important differences between juvenile and adult onset disease.
Juvenile SpA predominantly affects the peripheral joints and the incidence of axial arthritis increases with age. Enthesitis is important in early disease. This review article highlights the similarities and differences between juvenile and adult SpA including classification, pathogenesis, clinical features, imaging, therapeutic strategies, and disease outcomes. In addition, the impact of the biological transition from childhood to adulthood is explored including the importance of musculoskeletal and immunological maturation.
We discuss how the changes associated with adolescence may be important in explaining age-related differences in the clinical phenotype between juvenile and adult SpA and their implications for the treatment of juvenile SpA. The spondyloarthropathies SpAs are a heterogeneous group of inflammatory arthropathies affecting both the peripheral and axial joints. Other forms of SpA include psoriatic arthritis, enteropathic arthritis, reactive arthritis, and undifferentiated SpA 1.
Apart from axial and peripheral arthritis, common clinical features across all these subtypes can include enthesitis, dactylitis, and extra-articular manifestations such as acute anterior uveitis, inflammatory bowel disease IBD , and psoriasis. There is a strong association between these conditions and the major histocompatibility complex MHC class 1 antigen human leucocyte antigen HLA -B27 although the mechanism for this association remains unclear 2. The prevalence of SpA varies widely by geographical area with the highest rates reported in North America and Europe which may correspond to the prevalence of HLA-B27 3.
The onset of SpA occurs across a broad age range from childhood to adolescence and adulthood with a peak incidence in late adolescence and early adulthood 4. Although the common features remain the same, the clinical phenotype is different across the ages with peripheral arthritis and enthesitis predominant in juvenile SpA JSpA and axial manifestations more typical of adult onset disease. JSpA is classified differently from adult SpA as enthesitis related arthritis ERA which encompasses both axial and peripheral arthritis, and juvenile onset psoriatic arthritis, both of which are classified within the umbrella term juvenile idiopathic arthritis JIA 5.
