Juvenile Spondyloarthritis / Enthesitis Related Arthritis (SpA-ERA)

1.1 What is it? Juvenile SpA-ERA constitutes a group of chronic inflammatory diseases of the joints (arthritis), as well as tendon and ligament attachments to certain bones (enthesitis) and affects predominantly the lower limbs and in some cases the pelvic and spinal joints (sacroiliitis buttock pain and spondylitis back pain). Juvenile SpA-ERA is significantly more common in people that have a positive blood test for the genetic factor HLA-B27. HLA-B27 is a protein located on the surface of immune cells. Remarkably, only a fraction of people with HLA-B27 ever develops arthritis. Thus, the presence of HLA-B27 is not enough to explain the development of the disease. To date, the exact role of HLA-B27 in the origin of the disease remains unknown. However, it is known that in very few cases the onset of arthritis is preceded by gastrointestinal or urogenital infection (known as reactive arthritis). Juvenile SpA-ERA is closely related to the spondyloarthritis with onset in adulthood and most researchers believe these diseases share the same origin and characteristics. Most children and adolescents with juvenile spondyloarthritis would be diagnosed as affected by ERA and even psoriatic arthritis. It is important that the names "juvenile spondyloarthritis", "enthesitis-related arthritis" and in some cases "psoriatic arthritis" may be the same from a clinical and therapeutic point of view.