Summary

The spondyloarthritides (SpA) represent a combination of pathogenically related diseases that share many clinical manifestations. As a group, the prevalence of SpA is 0.5% to 1.9%, and the most common subgroups are ankylosing spondylitis (AS) and undifferentiated spondyloarthritis (uSpA). The typical age of onset of AS is between 20 and 30 years of age. Several studies have shown that there may be a delay of 5 to 10 years before diagnosis [Khan MA. Ann Rheum Dis 2002; Mau W et al. J Rheumatol 1988; Feldtkeller E et al. Rheumatol Int 2003].