Imaging of the seronegative spondyloarthopathies.

The seronegative spondyloarthropathies are a diverse group of conditions most commonly affecting the axial spine, often presenting with back pain of an inflammatory nature. The primary unifying feature of these disorders is sacroiliitis. The distinction between subtypes of spondyloarthritis is based on genotype (HLA-B27 positivity as in ankylosing spondylitis), peripheral manifestations of disease (psoriatic and reactive arthritis), and factors such as age, gender, and comorbidity. Although radiography has long been used to diagnose the spondyloarthropathies, advanced imaging with magnetic resonance is better able to diagnose these disorders at their earliest stages and monitor disease-modifying therapies.