Within the MIF gene promoter, two polymorphisms, a G>C single nucleotide polymorphism 270 bases before MIF transcription start (−270) (originally described as −173; HGVS nomenclature: NM_002415.2 c.−270G>C, rs755622) and a CATT tetranucleotide repeat CATT5-7 (rs3063368), have been associated with disease severity of multiple chronic inflammatory diseases, including osteoporosis, ankylosing spondylitis, and multiple sclerosis [6,7,8]. This evidence concerns the gene MIF and ankylosing spondylitis.