[HLA-B27 associated spondyloarthritis in childhood]

Ankylosing spondylitis, indefinite juvenile spondyloarthritis (JSA), reactive arthritides, psoriasis arthritis, arthritis of inflammatory bowel disease, and probably other rare diseases, such as the Behçet-syndrome, are sharing several distinctive features which discriminate them as a group from other arthritides, particularly from the rheumatoid arthritis in children (JRA) and adults. These distinctive features are: familial aggregation; association with HLA-B27; enthesopathy, sacroiliitis; predominance of Lower-Limb-arthritis; onset mostly after the age of 10 years, and typical manifestations of the skin and mucous membranes. Based on these characteristics and the probability of a later involvement of the spine, this group of diseases has been designated "HLA-B27-associated spondyloarthritides". Two thirds of all cases do not fit in any of the well-known spondyloarthritides. In this subgroup, designated as JSA, the disease begins usually with oligoarthritis and/or enthesopathy, and based on further clinical criteria it can early be distinguished from the JRA. The diagnosis of the other spondyloarthritides can be established primarily or later on follow-up, based on further characteristic symptoms and findings. In the differential diagnosis of arthritis in children, one third do have a spondyloarthritis and about one half do have JRA. This differentiation is of an important therapeutic and prognostic value, e.g. the slow-acting drugs are effective in JRA but not in spondyloarthritis, and in patients with axial manifestations, the early education and training for correct posture is important to prevent the development of kyphosis.