Radiology of seronegative spondyloarthropathies.

Radiographic manifestations of the seronegative spondyloarthropathies superficially resemble the findings of rheumatoid arthritis although they differ in both distribution and pattern of disease. Ankylosing spondylitis has a predilection for the axial skeleton; psoriatic arthritis may involve distal interphalangeal joints; and Reiter's syndrome is most commonly associated with asymmetrical lower extremity alterations. The absence of osteoporosis and the presence of bony proliferation are also noted in these disorders. Sacroiliitis and spondylitis, which can be observed in any of these disease, may have distinctive features. In ankylosing spondylitis, bilateral saroiliac joint alterations and typical syndesmophytes are common; in Reiter's syndrome and psoriasis, asymmetrical saroiliac joint changes and bulky spinal outgrowths may be observed. The physician should be aware of typical roentgen findings in each of the spondyloarthropathies.