When many people think of Jewish genetic disorders, Tay-Sachs disease comes to mind. But a disorder that impacts many more individuals with Ashkenazi Jewish heritage is Crohn’s disease. First identified by physicians at Mount Sinai Hospital in New York in 1932, Crohn’s disease is a type of inflammatory bowel disease and is characterized by intestinal inflammation causing pain, diarrhea, and weight loss.

The CDC estimates that over 600,000 Americans have the Crohn’s disease; there is currently no permanent cure. Research dating beginning in the 1990’s has shown that Crohn’s disease is 5 to 7 times more prevalent among Ashkenazi Jewish individuals, and that siblings and children of Jewish patients with Crohn’s disease are more likely to develop the condition than relatives of non-Jewish ones. Although the reasons for this difference are poorly understood, they are almost certainly genetic, rather than the result of behavior or environment.

A definitive international research study in November 2012 showed that there is overlap between genes related to IBD and genes involved in fighting infection by bacteria, therefore suggesting a historical connection between the two diseases. Specifically, it is conceivable that tuberculosis, which was a major presence in human civilization throughout history, drove natural selection to favor people with more active immune systems.

Around 100 years ago, tuberculosis was eliminated as a major health concern in the developed world, and those who had over-active immune systems — but who no longer had an infection to fight — instead manifested autoimmune diseases like Crohn’s disease. It is possible that this hypothesis extends to the Ashkenazim: throughout most of the history of the Ashkenazi population, Jewish individuals were more likely than other Europeans to live in urban cities and towns, rather than villages and countryside. This might have led to greater exposure to tuberculosis, and a greater shift in the gene pool towards having active immune systems. This, in turn, could have led to a more dramatic increase in Crohn’s disease starting in the early 1900’s for the Jewish population. While this remains purely a hypothesis, a study from 1903 in New York City showing that Jews who were infected with tuberculosis were only one-third as likely to die from it, compared to others living in the city.

At the Yale University Inflammatory Bowel Disease Program, we have been pulling together expertise in various fields to study this question and understand specifically the reasons for the greater Crohn’s disease risk in the Ashkenazim. We invite individuals of Ashkenazi Jewish heritage who have been diagnosed with Crohn’s disease to participate in our research via mail at no cost; interested patients can contact us at ibd@yale.edu or (203) 785-7573. With your help, we are working towards new and improved treatments for all who are living with Crohn’s disease.

This study is approved by the Yale Institutional Review Board HIC# 0607001669.

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