S100A8 and ankylosing spondylitis: The serum S100A8/A9 complex has been shown to be associated with disease activity in inflammatory diseases such as rheumatoid arthritis [20, 21], adult-onset Still’s disease [22], Sjögren’s syndrome [23], ankylosing spondylitis [24], Crohn’s disease [25], and ulcerative colitis [26].