[Spondyloarthritides].

The spondyloarthritides (SpA) are an interrelated group of rheumatic diseases that are characterized by common clinical symptoms and genetic similarities. The most important subtype is ankylosing spondylitis (AS), which is now considered part of axial spondyloarthritis. Important clinical features of the SpA are inflammatory back pain (IBP), asymmetric peripheral oligoarthritis, predominantly of the lower limbs, enthesitis, and specific organ involvement such as anterior uveitis, psoriasis and chronic inflammatory bowel disease. For clinical purposes, five subgroups are differentiated: AS, psoriatic SpA (PsSpA), reactive SpA (ReSpA), SpA associated with inflammatory bowel disease (SpAIBD) and undifferentiated SpA (uSpA). AS usually starts in the sacroiliac joints at a mean age of 26 years, affecting men slightly more frequently than women. SpA are genetically linked (90% of cases), the strongest contributing factor being HLA B27.Conventional radiography remains the gold standard for diagnosis in the axial skeleton. The new ASAS classification criteria have helped to improve the early diagnosis of SpA, with MRI and early HLA B27 determination playing an important role.