Straightforward answers to
Jewish individuals whose ancestors were from Germany, Russia, the Ukraine, Poland, and Hungary are typically Ashkenazi. The majority of Jewish families who migrated to the United States after the early 1800's are Ashkenazi. Sephardic Jews are those whose ancestors were Spanish or Portuguese prior to the Inquisition. Most Sephardic Jewish families in the United States either emigrated from Israel, Latin America, Central Asia, or the Middle East relatively recently, or emigrated from Holland, Portugal, or Spain as early as the mid-1600's. Jews who are neither Sephardic nor Ashkenazi are known as Oriental or Mizrahi Jews and live mainly in the Middle East.What disorders are we talking about?
Tay-Sachs disease, Canavan disease, and familial dysautonomia are the three most frequent serious conditions found mainly or exclusively in Ashkenazi Jews. Carrier screening for these is recommended by the American Congress of Obstetricians and Gynecologists (ACOG) as well as the American College of Medical Genetics (ACMG). Additional diseases for which carrier screening is available include Niemann-Pick (type A) disease, Fanconi anemia (group C), Bloom syndrome, Gaucher disease (the non-neuronopathic type), mucolipidosis type IV, maple syrup urine disease, lipoamide dehydrogenase deficiency, familial hyperinsulinism, nemaline myopathy, Usher syndrome types III and IF, Joubert syndrome, Walker-Warburg syndrome, and glycogen storage disease type 1a. Except for Tay-Sachs disease, which is also found in persons of French-Canadian (Acadian) ancestry, Irish ancestry, and rarely in mixed Jewish/non Jewish couples, both parents of nearly all affected individuals have at least some Ashkenazi ancestry.] Although not strictly a disorder of European Jews, cystic fibrosis is often included in an Ashkenazi heritage screening panel, since it occurs with the same frequency in European Jews as in members of the non-Jewish Caucasian population (approximately 1/2,500). Except for Tay-Sachs disease and cystic fibrosis, these disorders are uncommon in Sephardic and Mizrahi Jews.How are these conditions inherited?
All are autosomal recessive, which means both members of a couple must be carriers of the same condition in order to have an affected child. There are no outward physical manifestations in persons who are carriers for any of these disorders. When both parents are carriers for the same disorder, the risk of an affected child is 25% for each pregnancy. Prenatal diagnosis is available for such "at risk" couples. In some cases carrier screening is desired prior to marriage to assist in determining if a potential spouse is suitable.Are these diseases serious?
Definitely. Nearly all are either untreatable, or treatment is inadequate to prevent serious signs and symptoms. Many cause mental retardation or neurologic problems. Some may not be apparent or diagnosed before a woman becomes pregnant again. Cystic fibrosis is a condition that results in chronic lung disease (see Cystic Fibrosis: information for patients ).When and how should screening be performed?
Ideally, screening results (which typically take 1-2 weeks) are available prior to, or early in pregnancy. This allows enough time for planning, should either or both members of a couple are discovered to be carriers. It is usual to screen one member of a couple at a time, reserving testing for the other if he or she is identified as being a carrier; however, if time is critical, it is preferable to screen both members of a couple simultaneously. Carrier screening can be ordered individually by disease, as a panel of Ashkenazi diseases, or as part of pan-ethnic screening .Do I have to take these tests?
No! It is entirely your choice. Geneticists, physicians, and rabbis have been recommending that Ashkenazi Jewish couples have Tay-Sachs carrier testing for decades, and most encourage screening for additional disorders. In any case, the decision should be made by the individual(s) after being given all of the relevant information. Your obstetrician should have written information on Ashkenazi heritage carrier testing. If desired, your obstetrician can make a referral to a geneticist. The geneticist, after obtaining a complete family history and reviewing relevant medical information, will be able to discuss the issue in more detail, arrange the actual carrier testing, interpret the results of testing, and make recommendations for further testing and/or prenatal diagnosis.
Information for Health Professionals
Services | Insurance | Directions | Glossary | Genetics links | Topics of Interest | Our Staff | Pictures | Contact us | Home
© 2001, 2003 The Genetics Center, Inc, All Rights Reserved. Last updated February 11, 2013