The two main forms of inflammatory bowel disease (IBD), ulcerative colitis (UC) and Crohn's disease (CD) are characterized by chronic intestinal inflammation and risk of progression to colon cancer. One proposed cause of the latter characteristic is chromosome instability, since the rearrangement of genetic material can lead to activation of oncogenes, loss of tumor suppressor genes and other changes that lead to uncontrolled cell growth. Chromosome instability is particularly associated with UC and has been observed in colon epithelial cells and peripheral blood mononuclear cell. Since genomic instability in peripheral blood mononuclear cells (PBMCs) has been used as a biomarker for global cancer risk in a number of diseases, the latter observation suggests the possibility of a chromosome instability syndrome in UC that could affect all tissues. One possible cause of chromosome instability is telomere dysfunction .