Ankylosing spondylitis is caused by Klebsiella. Evidence from immunogenetic, microbiologic, and serologic studies.

Ankylosing spondylitis is a form of reactive arthritis following Klebsiella infection, usually occurring in an HLA-B27-positive individual. This conclusion is based on evidence obtained from several disciplines: immunogenetic studies show that there is molecular mimicry between HLA-B27 and Klebsiella; increased isolation of fecal Klebsiella has been reported in both Europe and North America; and finally, antibodies to Klebsiella have been demonstrated in ankylosing spondylitis patients in England and Finland. It is suggested that therapeutic trials should be set up with the aim of eliminating Klebsiella microbes, in an endeavor to test the validity of this theory.