Ulcerative colitis is linked to overgrowth with pathogenic microbes, the same as Crohn's disease, osteoporosis and
ankylosing spondylitis. In ankylosing spondylitis the vertebra of the spine fuse together causing stiffness and pain. Other joints may in time become affected.
Klebsiella, another type of pathogenic bacteria, produces a molecule that is similar to a tissue type found in people with this disease.