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."