Why did I get UC?
One of the most common questions posed by patients about their disease is: Why did I get UC?
Our current understanding is that inflammatory bowel disease (IBD) develops in genetically susceptible individuals when they are exposed to an environmental trigger that sets off an exuberant inflammatory cascade. Although most people with a new diagnosis of IBD do not have a family history, there is compelling evidence for a genetic contribution to this disease, further supported by the discovery of genes associated with IBD in the last five years. Approximately 5-25% of patients with IBD report having a family member who also has IBD (either Crohn’s disease or UC). Siblings of patients with UC are 5-15 times more likely to develop IBD than individuals without an affected brother or sister. Studies of identical twins have shown that if one twin has UC, there is a 10-20% probability of the other twin also developing UC. With regard to fraternal twins, however, the risk is the same as that for non-twin siblings. If one parent has UC, the chance of his/her child developing IBD is about 5%. In the special instance that both parents have IBD, the likelihood of their children having IBD increases to about 30% by age 28. Research has shown that there is concordance (similarity) of disease type among family members. That is, within families with one or more family members affected by IBD, individuals are likely to have the same form of disease as one another (Crohn’s disease or UC). Some studies have suggested that individuals with a family history of IBD may have earlier disease onset compared to individuals without affected family members.
Other factors influencing genetic risk include ethnic/racial background. The highest rates of IBD are found in Caucasian individuals, especially those of Jewish heritage. Among Jewish sub-groups, Ashkenazi Jews have a 2 to 9 fold greater prevalence over non-Jewish counterparts. African Americans and Asians are believed to have a lower risk of IBD, although there appears to be a trend towards growing prevalence rates in these populations.
While investigators have identified a handful of genes which may play a role in UC, no single gene alone has been established as a cause. Research has shown that the genetics of IBD are complex, most likely involving interactions of multiple genes and environmental factors. It is hoped that a better understanding of the interplay between genes and the environment will help identify what triggers IBD and how we may either prevent or treat it more effectively.