The term seronegative spondyloarthritides (SpA) is used to refer to a family of inflammatory rheumatic diseases characterised by inflammation of axial joints, asymmetric oligoarthritis and enthesitis, sometimes involving nonarticular structures, such as skin, heart, aortic valve, eye and kidney. The SpA consist of the following entities: ankylosing spondylitis, reactive arthritis, psoriatic arthritis, spondyloarthritis associated with IBD and undifferentiated spondyloarthritis. The prevalence of SpA in the population is 0,5-2%.