The juvenile-onset spondyloarthritides.

The juvenile-onset spondyloarthritides comprise a group of HLA-B27-associated disorders, which are mainly characterized by enthesitis and arthritis affecting the lower extremities, and in a variable proportion of cases, the sacroiliac and spinal joints. Additional features include a variety of extra-articular manifestations, and in some cases, bacterial infections as triggers. Except for the prevalence of some clinical features at onset and severity throughout the course of the disease, juvenile-onset SpA resemble their adult counterpart in most clinical aspects, strength of HLA-B27 association, and the role of arthritogenic bacteria in their pathogenesis. Not surprisingly, several aspects, from nomenclature to classification, and diagnostic criteria reflect to some extent those developed in the adult onset populations.