New clinical and radiographic features of the seronegative spondyloarthropathies.

This article reviews new data supporting the hypothesis that the clinical spectrum of the seronegative spondyloarthropathies is wider than previously realized. It describes the literature in general and specific reports on the prevalence and clinical features of seronegative spondyloarthropathies in a number of different populations from America and Asia. Undifferentiated or unclassified spondyloarthropathies are now recognized more frequently. There is an extensive analysis of new proposals for nomenclature and criteria for classification that need to be validated. The normal appearance and biomechanics of the sacroiliac joints as well as new imaging techniques to approach them in several diseases are also discussed. Clinical, radiographic, and histopathologic findings in spinal disease and further observations on gut inflammation and intestinal permeability are also presented here. A long list of clinical associations of the seronegative spondyloarthropathies is also given.