Frequently asked questions about the risk to other family members of developing IBD when a relative has CD or UC

If someone has IBD, how likely is it for someone else in his or her family to have the disease?

Studies that have looked at large numbers of families of Ashkenazi Jewish patients where an individual (known as a proband) has CD or UC, have shown that around 20% of probands have an affected relative.

If a parent has IBD, how likely is it for their children to develop the condition?

Having a positive family history is the greatest risk factor for developing IBD. First-degree relatives (children, siblings or parents) of an IBD proband are thought to have a lifetime risk of developing IBD of approximately 5-15%. This compares with a risk of 0.3% in the general (non-Jewish) population.

Is a child or a sibling of a proband with CD or UC, more likely to get CD or UC?

A family history is more frequent in individuals with CD compared to individuals with UC. If the proband and the relative have the same type of IBD, e.g. both have CD or both have UC, then the familial IBD is considered to be concordant, whereas if they have different types of IBD, i.e. one has CD and one has UC, then it is considered discordant. While affected relatives may develop either form of IBD, it is most likely that relatives will be concordant for disease type. CD in a first-degree relative of a UC proband is more likely than UC in a first-degree relative of a CD proband.

What is the risk of developing IBD for a more distant relative of an affected individual?

The risk for second-degree relatives (niece, nephew, grandchild, uncle, aunt) has been less extensively studied but is thought to be approximately three times higher than the population risk.

If both the parents have IBD, what is the risk to their offspring?

The risk to children of couples where both the parents have IBD is much higher than the risk where only one parent has IBD. It is thought to be about 1 in 3.

Is IBD more common in the Jewish population?

It has been reported in many different studies covering many different geographical locations that the Ashkenazi Jewish population have an approximately 4-fold increased prevalence of IBD compared to that of other Europeans and North Americans.

How many Jews have IBD in the UK?

According to the 2011 Census results for England and Wales, there are approximately 260,000 Jews in the UK, 95% of whom are thought to be of Ashkenazi origin. This is likely to be an underestimate and the figure is probably closer to 280,000.  Assuming a prevalence of approximately 1.2% in the Ashkenazi Jewish population (most recent figures assume up to 0.3% prevalence of IBD in the West), then there are estimated to be at least 3,360 Jewish individuals with IBD in the UK.