Reactive arthritis, a missing link: comment on the recent article from Sepriano

The recent paper from Sepriano et al provides an extremely important new insight on the concept of axial spondyloarthritis (axSpA).1 Clearly, the Gestalt of axSpA is heterogeneous, with three recognisable clinical entities labelled as: ‘pure axial SpA’, ‘axial SpA with peripheral signs’ and ‘axial SpA at risk’. The finding given in the paper suggests a larger overlap between axSpA and pSpA than anticipated at the time when the Assessment of SpondyloArthritis international Society (ASAS) criteria were developed. Thus, the question arises as to how accurately the three recognisable clinical entities of the ASAS classification criteria represent the diseases entities originally lumped together in the historical concept of SpA. The unifying historical concept of SpA lumps together an inter-related yet heterogeneous group of disorders which includes ankylosing spondylitis …