Ask the Genetic Counselor:
Meredith Seidel, MS, LCGC
Question from Nancy in Acton, MA
"I understand that Ashkenazi Jews have a one-in-forty chance of inheriting a BRCA gene mutation. What is the risk to Sephardic Jews?"
Response from Meredith Seidel, MS, LCGC
Massachusetts General Hospital Cancer Center
"Based on the data we have today, there is no definitive answer to this question. The 1/40 risk to carry a BRCA1 or BRCA2 gene mutation among Jews of Ashkenazi heritage refers to the risk of carrying what is known as a founder mutation: one of three specific gene mutations that can be traced back hundreds of years to the earliest known Ashkenazi ancestors. Studies done on families thought to be of “pure” Sephardic ancestry have identified possible founder mutations in this group as well. However, the prevalence of those mutations is difficult to establish because the number of individuals studied is relatively small.
The question of heritage is further complicated by its variable definition. For example, some individuals may define themselves as Sephardic based on the customs and traditions upheld by their family; however, their ancestral roots (the origin of their DNA) may be, at least in part, Ashkenazic.
For these reasons, as a genetic counselor, I err on the side of caution. If someone reports Jewish ancestry of any type, I incorporate that information into my assessment of their risk regardless of whether they specifically identify themselves as Ashkenazi."
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