Jewish genetic diseases are a group of rare autosomal recessive disorders that are far more prevalent among people with Jewish ancestry than in the general population. Autosomal recessive diseases are transmitted genetically by carrier parents who themselves do not suffer from the disorder but carry the genes that can cause the disease. When two carriers of a genetic mutation associated with a particular disorder have children together, each of their offspring has a one in four chance of developing the disease and a 50 percent chance of becoming carriers themselves.
As many as one in three Ashkenazi Jews are estimated to be carriers for one of about 19 genetic diseases. In all, Jews have higher carrier rates for more than 40 genetic diseases. These include better-known disorders such as Gaucher disease, Cystic Fibrosis and Tay-Sachs, along with far rarer conditions like Nemaline Myopathy and Walker Warburg. Sephardic and Mizrahi Jews are also at risk for some genetic diseases, but these generally vary with the particular country of origin and do not affect Sephardic Jews as a whole. There are no known genetic diseases specific to Ethiopian Jews.
While some Jewish genetic diseases can be effectively managed to permit those affected to lead mostly normal lives, none is curable and some are invariably fatal.
Certain diseases are believed to be more common among Jews because of the so-called founder effect, in which genetic diversity is reduced when a population descends from a small number of common ancestors. Moreover, since Jews historically have tended to marry only Jews, those mutations weren’t passed along to other groups, and they weren’t lessened by the introduction of new genes.
The best protection against these diseases is carrier testing, and there has been a broad push in recent years to make such testing standard practice for Jewish couples prior to pregnancy, and even prior to marriage. The incidence of some diseases has been reduced dramatically since genetic screening first became available in the 1970s.
Pronounced: seh-FAR-dik, Origin: Hebrew, describing Jews descending from the Jews of Spain.