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Huntington's
Disease and Childbearing
Katherine Harris
The State University of New York
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To begin with I think such would be a personal choice as to whether to try conceiving
a child with a family history of Huntington's disease. More important, there are options available to couples wanting a genetically
inherent child of their own.
1. Huntington's disease (HD) is a rare inherited neurological disorder caused by a defect in a single
gene. It hits victims in middle age, after they have had children and therefore passed the gene on. It gets progressively
worse, causing brain damage leading to involuntary movements, mental deterioration and death 15-20 years later.
A possible treatment for HD has been developed using hamster kidney cells genetically engineered to
produce a naturally occurring nerve growth factor that protects brain cells. These were injected into the brains of monkeys
and found to protect them from brain damage in the areas affected by HD.
2. At risk women who are pregnant may wish
to take a prenatal test to permit the selective abortion of a fetus found to be a gene carrier for Huntington's disease. Yet,
when it comes to testing, testing is based on genetic linkage, direct gene testing will have a significant impact on individuals
and their families, especially spouses and parents. Sensitivity to this fact remains an important prerequisite for testing.
The
testing process is necessary and based on current knowledge of Huntington's disease and sound psychological principles.
Experience has shown this process to be effective in minimizing serious outcomes resulting directly
from testing. |
3. Prenatal testing can be used to increase the fetal risk from 50% to virtually
100% or to decrease the fetal risk from 50% to virtually zero.
Options for decision making, including the option of termination should the fetus be found to be a
gene-carrier, should be discussed prior to testing. The potential difficulties of having a child identified as a gene-carrier
from birth (expectations, discrimination, insurance problems, psychological problems) should also be discussed.
4.
The second circumstance is where the parent is at 50% risk and is not showing symptoms. In this case, to find that the fetus
carries the gene for Huntington's disease automatically reveals that the parent is a gene-carrier as well.
A very common and problematic circumstance involves an at risk woman who is
pregnant and who undergoes pre-symptomatic and prenatal testing simultaneously. If the outcome is positive for
both tests, the impact is overwhelmingly traumatic.
Prospective parents should be clearly counseled about the emotional ramifications of this potential
double whammy. A two-step process by which the at risk parent is tested first and prenatal testing is done second if necessary,
is probably the preferred option.
5. Since non-disclosing prenatal testing relies on genetic linkage analysis and therefore
requires DNA samples from several family members, it is particularly important for couples seeking this type of test to seek
counseling and to prepare for the test prior to conception.
If possible, the necessary blood samples should be obtained and DNA analysis initiated in advance
of the pregnancy. Fetal DNA samples are obtained by Chorionic Villus Sampling (CVS) or Amniocentesis. |
Sources:
1. Scherzinger E, Lurz R, Turmaine M
et al (1997) Huntington-encoded polyglutamine expansions form amyloidal-like protein aggregates in vitro and in vivo. Cell
90 (3): 549
2. Emerich DF, Winn SR, Hantraye PM, Peschanski M, Chen E-Y, Chen Y, McDermott P, Baetge EE & Kordower
JH (1997) Protective effect of encapsulated cells producing neurotrophic factor CNTF in a monkey model of Huntington's disease
Nature 386: 395 date cited: 04/07/03
3. Guidelines for Genetic Testing for Huntington's
Disease (Revised 1994) Huntington's Disease Society of America, Inc date cited: 04/07/03 |
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