Similarities and differences between nonradiographic and radiographic axial spondyloarthritis

The concept of axial spondyloarthritis with two forms or subtypes (nonradiographic and radiographic) has been established over the last few years. However, debates concerning especially the nonradiographic form of the disease are still ongoing. Here we summarise recent data on similarities and differences (and their possible explanations) between nonradiographic axial spondyloarthritis and radiographic axial spondyloarthritis (ankylosing spondylitis).