Local News

When genetic screening may be necessary

By Janis Siegel, JTNews Correspondent

    In the time it

    takes to draw a small sample of blood in a doctor’s office,

    Ashkenazi Jews, whether they are of full or partial Jewish

    ancestry, can take a genetic test that will identify whether

    or not they are carriers of the genetic mutations for eight

    chronic and deadly diseases that disproportionately affect

    them.

   

    Touting a 99.5

    percent accuracy rate, for approximately $300 per test –

    depending on the lab – a couple having a child can be

    genetically screened for diseases like Tay-Sachs, cystic

    fibrosis, Canavan disease, Fanconi anemia (Type C), Niemann-Pick

    (Type A); Bloom’s syndrome; familial dysautonomia and

    Gaucher disease (Type 1), the only one of the eight that

    typically onsets in adults, later in life.

   

    "These eight

    diseases are inherent," said Nancy Shu, a genetic counselor

    in Perinatal Medicine at Swedish Medical Center who counsels

    many Jewish couples of Ashkenazi background on a daily

    basis. "Even if one partner is Jewish and the other is not,

    they may still be a carrier."

   

    Type A Tay-Sachs

    disease is a progressive neurological condition that

    typically appears by six months of age. The symptoms of Tay-Sachs

    include loss of coordination, blindness, deafness, seizures

    and severe mental retardation. Children with Tay-Sachs have

    a three to five-year life expectancy. Approximately one in

    25 Ashkenazi Jews are carriers.

   

    Children born

    with Type A Niemann-Pick disease, a group of

    neurodegenerative disorders whose symptoms include

    enlargement of the liver and spleen, poor growth and loss of

    brain function, have a two to four-year life expectancy. The

    carrier rate among Ashkenazi Jews is one out of 90.

   

    Canavan disease,

    another neurological disorder, includes symptoms like

    generalized weakness, severe mental retardation, and

    enlarged head size. The disease usually begins in infancy

    and is typically fatal within the first decade, although

    some children live to be teens and some reach their early

    20s.

   

    According to the

    Jewish Genetic Diseases program information at the Saint

    Barnabas Health Care System in Livingston, New Jersey,

    results from genetic screening typically take two to three

    weeks.

   

    Two carriers

    having a child together have a 50 percent chance of having a

    child who is a carrier and a 25 percent chance of having a

    child with the identified disease or gene mutation.

   

    "When that is the

    case," said Shu, "I offer couples amniocentesis. If the

    amniocentesis shows the child has the gene, then it’s

    definitive." At that point, couples must face some tough

    decisions.

   

    "Some couples may

    choose to terminate the pregnancy, some may choose to plan

    ahead for their baby’s special needs," said Shu. "Others

    take the test just to give them peace of mind and rule it

    out."

   

    SBHCS research

    also shows that cystic fibrosis, a chronic illness of the

    respiratory and gastrointestinal systems, is found in all

    ethnic groups but is very common in Ashkenazi Jews.

   

    There is no cure

    for cystic fibrosis, and although some patients may live up

    to the age of 30, others live only to adolescence and the

    general life expectancy varies greatly from patient to

    patient.

   

    "If an Ashkenazi

    Jewish couple comes to me, I would recommend they get

    screened for cystic fibrosis," said Shu. "Some people decide

    to be tested for all genetic mutations and others choose to

    only test for a particular gene."

   

    If amniocentesis

    is called for in order to screen for the gene in the fetus,

    Shu also has to warn the couple that the procedure is not

    without its own risk.

   

    "The

    amniocentesis procedure itself leads to miscarriage in one

    out of every 400 women," she said.

   

    In addition to

    carrier screening, prenatal testing and newborn screening,

    SBHCS says that genetic tests are used for several other

    reasons, including testing adults to predict pre-symptomatic

    adult-onset of diseases, pre-symptomatic testing to assess

    the probability of developing adult-onset genetic disorders,

    cancers and Alzheimer’s disease, confirming a diagnosis for

    a person who is displaying symptoms, and for forensics and

    identification purposes.

   

    One of the most

    important reasons that adult Ashkenazi Jewish men and women

    have for getting screened is to detect the presence of the

    notorious BRCA1 or BRCA2 genes, both genetic markers for

    breast and ovarian cancers.

   

    While the general

    population runs a 12 percent risk of developing breast

    cancer and one percent risk of developing ovarian cancer,

    continues the SBHCS site, women who inherit mutant forms of

    BRCA1 may have up to an 85 percent risk of contracting

    breast cancer and a 44 percent risk of contracting ovarian

    cancer.

   

    They estimate

    that one out of every 50 Ashkenazi Jews carries a mutant

    copy of either gene.

   

    "Seattle has one

    of the highest rates of breast cancer in the U.S.," said

    Henry Kaplan, a medical oncologist who has been practicing

    at Swedish Medical Center since 1981. "We see a lot of

    Ashkenazi people in their 30s and 40s."

   

    Although

    Ashkenazi men with the genetic mutation seem to run a higher

    risk of developing breast, prostate and pancreatic cancer,

    Kaplan says that this is still a relatively controversial

    finding.

   

    "You only need to

    get the gene from one parent, but even then, a person still

    may not get the disease," said Kaplan. "But if you have the

    gene and you get the disease, someone with BRCA would get it

    earlier than someone without it."

   

    Although other

    types of mutations in BRCA1 and BRCA2 do exist in the

    general population, these two specific mutations that are

    associated with Ashkenazi Jews have not been found in the

    non-Jewish population.

   

    "A woman who

    finds she has the mutation but has not developed cancer

    might want to take preventative measures by taking

    medication or having her breasts or ovaries removed," Kaplan

    added. "If they develop cancer, they have a higher risk of

    getting it again."