The spondyloarthritides (SpA) are a group of related diseases comprising axial SpA (axSpA), namely non-radiographic (nr-axSpA) and radiographic axSpA (r-axSpA), psoriatic arthritis (PsA), arthritis/spondylitis associated with inflammatory bowel disease, reactive arthritis and undifferentiated SpA [1, 2] sharing clinical characteristics such as spondylitis, peripheral arthritis, enthesitis, dactylitis, uveitis or genetic association with HLA-B27. Nevertheless, each disease has its own clinical presentation with either a predominantly axial disease activity as in r-axSpA or a predominantly peripheral disease activity as in PsA.
