Ashkenazi Jewish (AJ) genetic screening has expanded significantly in the past 4 decades. Individuals of eastern European (Ashkenazi) Jewish descent are at increased risk of having offspring with particular genetic diseases that have significant morbidity and mortality. In addition, there are some disorders, such as cystic fibrosis (CF), for which northern European Caucasians are at comparable risk with those of an AJ background. Carrier screening for many of these Jewish genetic disorders has become standard of care. As technology advances, so does the number of disorders for which screening is available. Thus, we need to continue to be cognizant of informed consent, test sensitivity, confidentiality, prenatal diagnosis, preimplantation genetic screening, and public health concerns regarding testing.
HISTORY OF JEWISH POPULATIONS AND GENETIC EFFECTS

The Jewish people have a history spanning more than 2000 years.1 They are a migratory people and have established communities throughout the world. Three groups of Jews have been defined by their location of origin: Sephardic Jews (initially from Spain and later predominately northern Africa, the Balkans, Turkey, Lebanon, and Syria), Middle Eastern Jews (from Israel, Iraq, and environs) and Ashkenazi Jews (primarily of eastern European origin).Jews consider themselves a people because of their common religion, dialect, customs, and marriage within the community. Thus, they have maintained a group identity as well as a genetic identity.2 Many studies have shown that contemporary Jews share several chromosome markers and polymorphisms as well as genetic mutations.3–5 However, there is no such thing as a Jewish

Obstetrics and Gynecology and Women’s Health, Albert Einstein, College of Medicine, Bronx, NY, USA b Reproductive Genetics, Montefiore Medical Center, 1695 Eastchester Road, Suite 301, Bronx, NY 10461, USA c Obstetrics and Gynecology, North Bronx Healthcare Network, Bronx, NY, USA * Corresponding author. Reproductive Genetics, 1695 Eastchester Road, Suite 301, Bronx, NY 10461. E-mail address: sklugman@montefiore.org Obstet Gynecol Clin N Am 37 (2010) 37–46 doi:10.1016/j.ogc.2010.01.001 obgyn.theclinics.com 0889-8545/10/$ – see front matter ª 2010 Elsevier Inc. All rights reserved.

genome and Jews are more likely to share sequences with fellow non-Jews than with each other.2 Current estimates of the world’s Jewish population total 13 million, with the overwhelming majority in the United States and Israel. Most individuals of Jewish ancestry in North America are of Ashkenazi origin.6 Although there are disorders of significance in the non-AJ Jewish population, they are beyond the scope of this article. Testing in the non-AJ community remains limited at this time in the United States but for more information, the reader is directedto the review by Zlotogora and colleagues which provides information and links to relevant databases.
Founder Effects and Historical Origins

Many of the disorders in the AJ population can be attributed to mutations presumed to have each arisen in a single individual many centuries ago. This phenomenon had been coined the ‘‘founder effect’’8 or ‘‘genetic drift.’’ This phenomenon can occur when an individual with a relatively rare mutation moves with a small group to a new location and subsequently proceeds to undergo a significant population expansion. The once rare mutation will now be quite common in this new well-defined population group. The same effect can be seen if an individual with a relatively rare mutation is part of a group that is reduced from a once large population to a small group because of loss of members. Again, a once rare mutation will no longer be rare as the denominator (the total members in the group) has now severely contracted. Historically, Jews fell into both categories, as they were often forced to move to new locations or to endure pogroms that greatly lessened their numbers. Using molecular and bioinformatic tools, some investigators have even managed to determine the connection between some of these disorders and historical events in Jewish history.2 The founder effect is not limited to the AJ population and likely accounts for the higher rate of TaySachs disease (TSD) in French Canadians, although different mutations account for the disease in this population.
HISTORY OF JEWISH GENETICSCREENING AND TESTING

The history of Jewish genetic screening and testing begins with screening for TSD. The first prenatal detection of TSD was accomplished in 1969.9 A British ophthalmologist, Warren Tay, in 1881 as well as an American neurologist, Bernard Sachs, originally described the disease in 1887. Both physicians described a fatal disorder that presented in infancy with blindness, loss of motor function, and cerebral degeneration. Klenk, a German professor, in the 1940s reported the metabolic abnormality in TSD affected gangliosides, a new class of lipids. In the next several decades, the underlying defect in lysomal hexsaminidase A activity was elucidated thereby allowing testing of heterozygotes with somewhat decreased enzyme activity. In the early 1970s, physicians in several predominantly Jewish neighborhoods went door-to-door and collaborated with Jewish community groups to educate and screen Jewish women.10 Tay-Sachs was known to be of autosomal recessive inheritance whereby carriers were considered silent. Through education and community consultation, the stigma of being labeled a carrier was overcome and was such a success that children diagnosed with Tay-Sachs within the Jewish community have become a rarity to the extent that most children currently diagnosed with TSD are not of Jewish background do not have other identifiable risk factors.11 Proposed mechanisms include unknown AJ ancestry, lack of screening, or laboratory or physician error. In the early 1980s, Dor Yeshorim, also called The Committee forPrevention of Genetic Diseases, was started in the Ultra Orthodox community. This program
advocates anonymous testing, which is performed primarily on young adults. Those tested are given a special number and when 2 individuals contemplate marriage they contact Dor Yeshorim and are informed if their offspring would be at risk. This system has received some criticism but remains popular and has been effective in the Ultra Orthodox community. Like Tay-Sachs, the Jewish genetic diseases that are screened for today are of autosomal recessive inheritance. Thus, both parents must be carriers and they would not be aware of their carrier status without testing, as carriers do not have any symptoms. Screening does exist for several autosomal dominant disorders seen more frequently in Ashkenazi Jews, such as torsion dystonia familial breast and ovarian cancer, and familial colon cancer.14 However, because of the complexity of screening, penetrance, and serious implications for other immediate family members, individual genetic testing is recommended for those at high risk for these disorders and testing is not currently performed during the routine prenatal visit. Today, many Jewish women are screened in pregnancy for TSD and some of the other Jewish genetic disorders. However, preconception counseling is the ideal time for education and testing so that women have the broadest reproductive options available. Presently, existing barriers to preconception screening include provider education andsufficient time in a busy obstetric practice. Cost of testing may also be an issue as carrier testing for all the disorders can be expensive, potentially hundreds to thousands of dollars. Not all young people have insurance and some may have insurance that does not cover prenatal genetic testing outside of pregnancy. However, some insurance companies do cover preconception genetic testing when couples are seriously contemplating pregnancy.
THE JEWISH GENETIC DISORDERS

Jewish genetic diseases are rare, with an incidence of 1/900 to 1/40,000. However, approximately 1/5 Ashkenazi Jews will be a carrier for 1 of these disorders and approximately one-third of couples will have at least 1 carrier.15 Sensitivity for carrier testing for these disorders remains high as laboratories are screening for 1 to 4 founder mutations per disorder. Testing for Jewish genetic diseases has become more readily available and has rapidly expanded in the later half of this decade. Thus, the recommendations for testing and inclusion of certain disorders are also changing beyond TSD alone. In October 2009, the American College of Gynecology and Obstetrics (ACOG), through their Committee on Genetics, reconfirmed their previous recommendation to include TSD, Canavan disease (CD), CF, and familial dysautonomia (FD).16 In their committee opinion, ACOG added that individuals of AJ descent may inquire about the availability of carrier screening for other disorders such as mucolipidosis IV (MLIV), Niemann-Pick disease type A (NPD-A), Fanconi anemia group C (FA-C),Bloom syndrome (BS), and Gaucher disease (GD). The American College of Medical Genetics (ACMG) had previously recommended in 2008 that carrier screening be offered for TSD, CD, CF, FD, FA-C, NPD-A, BS, MLIV, and GD to all Jews of AJ background following a conference at which medical professionals and Jewish community groups shared a platform.15,17 The decision to include disorders beyond those required in the ACOG panel was based on the fact that some of the diseases have devastating outcomes (such as NPD-A) and more importantly, all have excellent detection rates with currently available technologies. Furthermore, broad testing has strong backing from the Jewish community.17

Both guidelines do share many elements in common, including individuals with a positive family history should be offered carrier screening and may benefit from genetic counseling. Also recommended in both documents is the importance of testing the Jewish partner even if only 1 member of a couple is of AJ background. Even though the non-AJ partner may not benefit from mutation testing specific to the AJ population, a geneticist can arrange for other testing, such as biochemical testing in the case of TSD or complete gene sequencing for other disorders, to determine if the individual is also a carrier of a specific disorder. Screening for other Jewish genetic diseases, such as glycogen storage disorder type 1A, maple syrup urine disease, dihydrolipoamide dehydrogenase deficiency, familial hyperinsulinism, nemaline myopathy, andUsher syndromes type I and III, are being routinely offered by providers and encouraged by laboratories that are not currently recommended by either the ACMG or ACOG.18–24 The disease prevalence of these 7 disorders is much less than TSD, CD, CF, and FD. Thus, the detailed discussion in this article is limited to those disorders for which prenatal screening is recommended by ACOG and/or ACMG (Table 1).
TSD (ACOG and ACMG

TSD is a neurodegenerative disorder that presents in the first year of life and is fatal in early childhood. It is caused by a deficiency in b-hexosaminidase A (Hex A) which in turn causes accumulation of a cell membrane glycolipid, Gm2 ganglioside, within the lysosome. Infants are classically macrocephalic because of storage material accumulation in the brain and have the characteristic cherry red spot on their macula. The incidence of TSD is 1:3000, with a carrier frequency of approximately 1:30.16 As previously mentioned, screening programs initiated in the 1970s have been widely successful, and have led to at least a 90% reduction in the incidence of TSD. Screening is based on a biochemical assay, whereby the actual Hex A enzyme is measured. As protein levels rather than ethnic-specific mutations are being analyzed, biochemical screening is an excellent test regardless of genetic background. Measurement in serum is particularly cost-effective; however, these levels in serum are altered in pregnancy and oral contraceptive use and can lead to excessive inconclusive reports. Therefore, in pregnancy or forwomen on birth control pills, leukocyte or platelet assay is preferred.25,26 DNA-only screening tests for the 3 most common mutations has previously been suggested as an alternative to biochemical testing in the AJ population, identifying 93% to 99% of carriers.27,28 However, these studies were done in a relatively homogeneous AJ population. A recent analysis of TSD by Schneider and colleagues26 in a population of self-identified AJ individuals concluded that Hex A enzyme levels were crucial in screening for this disorder as more than 10% of carriers would be missed using DNA only. With increasing intermarriage rates and diversity within the population, the National Tay-Sachs & Allied Diseases Association has confirm this recommendation in its 2009 position statement that biochemical and not DNA testing is preferred in this population.29
CD (ACOG and ACMG

CD is also a progressive neurodegenerative leukodystrophy. Onset appears within the first few months of life and is uniformly fatal in early childhood. The disease is caused by a deficiency of aspartoacylase, which leads to accumulation of N-acetylaspartic acid in the brain and urine. Infants have macrocephaly and seizures and the associated pathologic finding is spongy degeneration of the brain.30 Kronn and Oddoux31 suggested testing among Ashkenazi Jews in 1995 after a pilot program at New York University revealed a carrier rate in Ashkenazi Jews similar to that of TSD.


Table 1 Characteristics of AJ genetic diseases for which carrier testing is recommended DiseaseName Tay-Sachs Disease Canavan Disease Cystic Fibrosis Familial Dystautonomia Fanconi Anemia Type C Niemann-Pick Type A Bloom Syndrome Mucolipidosis IV Gaucher Disease Major Clinical Characteristics Enzyme deficiency, progressive neurologic disorder, death by age 4 y Progressive neurologic disorder, death in childhood although some survive longer Lung and gastrointestinal disorders, median survival 301 y Abnormal sensory and autonomic nervous system functioning, symptomatic treatment only Deficient bone marrow development and function. Rarely reach adulthood Storage disorder, mental and physical degeneration. Death by age 2 y for type A Skin, and growth abnormalities, cancer predisposition, death in young adulthood Lipid accumulation, eye issues, mental retardation Storage disorder, enlarged spleen, liver, anemia , bone pain. Life expectancy and severity varies. Enzyme therapy available Carrier Frequency 1/30 1/40 1/29 1/32 1/89 1/90 1/100 1/127 1/15 No. of Mutations Tested 3 2 5–7 2 1 3 1 2 4 Detection Rate 94–98a 98 97 99 99 95 95–97 95 95b Carrier Risk After Negative Resultc 1/484 to 1/1451 1/2000 1/1000 1/3101 1/8801 1/1781 1/1981 to 1/3301

Varies based on enzyme versus mutation analysis. May include homozygous asymptomatic individuals. Calculated using Bayesian statistical method.

The disease incidence is 1:6400, with a carrier frequency of 1:40.16 Carrier screening is based on identification of either of the 2 most common mutations inthe Ashkenazi population, and has a detection rate up to 98%.
CF (ACOG and ACMG

CF is a chronic debilitating disease affecting many organ systems, including the lungs, gastrointestinal tract, sweat glands, and the male reproductive tract. It is the most common single gene disorder in Caucasians. CF is caused by a mutation in the gene on chromosome 7 that encodes a protein called the CF conductance transmembrane regulator (CFTR), which in turn regulates the function of chloride channels. More than 1000 mutations have been identified in CFTR. The severity of disease is variable. Treatment is available and includes pancreatic enzymes, respiratory therapy, nutrition, and aggressive management of infection.32 In 2001, ACMG and ACOG introduced guidelines for prenatal and preconception carrier screening for CF and recommended that screening be offered to high-risk couples, such as Caucasians (including Ashkenazi Jews) who are planning a pregnancy. In 2005, ACOG reconfirmed these guidelines and introduced the concept of pan ethnic screening as most obstetricians were indeed offering CF screening to women of all backgrounds.33 Amongst AJ individuals, the disease incidence of CF ranges from 1:2500 to 1:3000, with a carrier frequency of 1:29. The common AJ mutations are included in the ACOG recommended screening panel and therefore adhering to ACOG guidelines will identify approximately 97% of CF mutations.
FD (ACOG and ACMG

Patients with FD have a sensorimotor neuropathy, resulting in inadequate development of the sensory andautonomic systems, which results in significant gastrointestinal reflux, lung disease, decreased pain and temperature perception, absence of tears and blood pressure abnormalities. FD presents in infancy and occurs almost exclusively in the AJ population. Carrier screening was recommended by ACOG in 2004.34 Treatment includes supportive care of all systems affected and can improve survival.35 The disease incidence for FD is 1:3600 with a carrier frequency of 1:32.16 Two mutations accounts for more than 99% of the mutations in the AJ people, however 1 mutation is responsible for most carriers.36 Greater than 99% of carriers and greater than 99% of affected fetuses can be identified.
FD-C (ACMG

FD-C is characterized by progressive bone failure, congenital anomalies (absent thumbs, radial hypoplasia, cardiac, renal, gastrointestinal, and neurologic abnormalities) and a predisposition to malignancy. FD-C is caused by a propensity to chromosome breakage and increased sensitivity to DNA cross-linking agents. Onset is variable, ranging from birth to 9 years. Patients can be treated with stem cell transplantation however median survival is only until the late teenage years.37 FD-C has an incidence of 1:32,000 and a carrier frequency in Ashkenazi Jews of 1:89.16 A single mutation is most commonly responsible in Ashkenazi Jews, and has not been found in any affected individual of non-Jewish ancestry. Screening would identify more than 99% of carriers.
NPD-A (ACMG

Like Tay-Sachs, NPD-A is a progressive neurodegenerative diseasewith onset in infancy and fatal in early childhood. It is caused by a deficiency of sphingomyelinase resulting in an accumulation of sphingomyelin in the lysosome. Infants present with

hepatosplenomegaly, hypotonia, and feeding issues. Cherry red spots are seen in the macula of half of the patients.38 NPD-A has an incidence of 1:32,000 and a carrier frequency in the AJ population of 1:90.16 Three mutations account for approximately 95% of mutations in the AJ people.
BS (ACMG

BS is a chromosomal instability disorder that presents in infancy and is characterized by short stature, impaired intellect, photosensitivity, and immunodeficiency. These patients have a predisposition to cancer, commonly leukemia and gastrointestinal malignancy. The median age of death is 28 years.39 BS is extremely rare in the general population, but has an incidence of 1:40,000 in Ashkenazi Jews with a carrier frequency of 1:100.16 A complex frameshift mutation accounts for more than 99% of the mutations in the AJ population.
MLIV (ACMG

Like TSD, MLIV is a lysosomal storage disease that is characterized by growth delays, severe mental retardation, and ophthalmologic abnormalities. This disease is caused by abnormal membrane endocytosis resulting in accumulation of lipids and mucopolysaccharides in the lysosome. Patients present early in childhood with developmental delay, intellectual impairment, and eye issues (corneal clouding and retinal degeneration). They can have a normal life span, however, mostaffected patients never attain language or motor function past the capacity of a 2-year-old.40 The incidence of disease is 1:62,500 and the carrier frequency in the AJ population is 1:127.16 Two mutations account for more than 95% of mutant alleles in Ashkenazi Jews. Screening would detect approximately 95% of carriers.
GD (ACMG

GD is also a lysosomal storage disorder caused by a deficiency in glucocerebrosidase resulting in an accumulation of glucosylceramide in the macrophages of the reticuloendothelial system of the liver, spleen, bone marrow, and lungs. It is subdivided into 3 types. Type 1, which has a wide range of expression, is the most common type found in Ashkenazi Jews. Onset may begin in early childhood and be characterized by bone fractures, hepatosplenomegaly, and thrombocytopenia. Many cases are mild or asymptomatic, and approximately half do not present until the age of 45 years. The average life expectancy is estimated to be 68 years.41 GD is the most prevalent genetic disorder amongst Ashkenazi Jews with an incidence of 1:900, and a carrier frequency of 1:15.16 Screening is based on the 4 most common mutations and detects approximately 95% of carriers. Some have questioned routine screening for this disorder because of the variable expression of the disease, the possibility of identifying asymptomatic affected individuals, and the availability of enzyme replacement therapy for management of the disease.42 However, there can be very significant morbidity associated with GD, including bone fractures in youngpeople. Furthermore, therapy is available but can be associated with significant cost. In addition, there is considerable support for screening within the community and families dealing with GD.17
CURRENT RECOMMENDATIONS

Ideally, screening should occur before conception. A general description of the disorders should be provided. Detailed descriptions of the particular disorders are not necessary and if a carrier is identified, such


discussions can take place at that time for the particular disorder in question. Audiovisual materials to help with overall education of couples are certainly appropriate. Individuals should be made aware that carriers are healthy and 1 in 5 people of AJ background will be a carrier. Ensure that there is an understanding of residual risk; no matter how good the test, there is a small possibility with DNA testing that a mutation is missed. If only 1 member of a couple is of AJ decent, that person should be tested first. If someone has a Jewish grandparent, testing is warranted. Formal genetic counseling should be facilitated if desired by an individual or if felt necessary by the obstetrician or health care provider. When a carrier is identified, this information has great import to the entire family. However, as explicitly stated in the ACOG guidelines the individual should be encouraged to contact family members. There is no provider-patient relationship with the relatives and confidentiality must be respected.

SUMMARY

Prenatal care providersmust be aware of the current recommendations for AJ genetic testing as put forth by ACOG. The ACMG recommendations are similar to those of ACOG in that both groups recommend testing for TSD, CD, CF, and FD. However, although ACOG states the patient may inquire about testing for FA-C, NPD-A, BS, MLIV, and BS, ACMG recommends screening. Providers must be able to recognize situations for which genetic counseling and/or prenatal diagnosis and/or preimplantation genetic screening would be appropriate. As technology advances and becomes more accurate and cost-effective, screening for even more disorders may be available in the future. Because TSD is no longer seen predominantly in the AJ community, it can be considered a disorder of the general population, albeit rare, with a carrier rate of approximately 1/300. However, despite this rare carrier frequency, there are calls from this community for pan ethnic screening. Although currently not recommended, screening for disorders once considered Jewish genetic diseases may one day become part of the obstetrician’s practice in the future as genetic knowledge continues to expand and marriage between racial and ethnic groups likewise can be expected to increase in the future.
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