Download Prenatal Diagnosis and Genetic Counseling

Genetic Counselling
By
Dr. Salah Jadallah
What Is Genetic Counseling?
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Genetic counseling is the process of:
evaluating family history and medical
records
ordering genetic tests
evaluating the results of this
investigation
helping parents understand and reach
decisions about what to do next
‫‪ ‬االستشارة الوراثية مهمة قبل الزواج‬
‫النها تساعد في كشف االمراض‬
‫الوراثية واالمراض التي تبقى منتقلة‬
‫من جيل الى اخر‬
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Genetic Counseling
strong communicative and supportive
element
‫‪ ‬إجراء فحوصات ما قبل الزواج والفحص‬
‫أثناء الحمل والفحص المبكر للمواليد‬
‫واالستشارة الوراثية تعد من أفضل‬
‫الوسائل للحد من انتشار األمراض‬
‫الوراثية التي ال يمكن عالجها بشكل‬
‫نهائي‬
Genetic counselor
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Genetic counselors can help identify and
interpret the risks of an inherited
disorder, explain inheritance patterns,
suggest testing, and lay out possible
scenarios.
He refers you to a doctor or a laboratory for
the actual tests.
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The best time to seek genetic
counseling is before becoming
pregnant, when a counselor can help
assess your risk factors. But even after
you become pregnant, a meeting with a
genetic counselor can still be helpful.
‫‪ ‬الهدف من االستشارة الوراثية للبحث في‬
‫تاريخ العائلة المرضي ومحاولة معرفة اذا‬
‫كان هناك امراض وراثية مثل وجود حاالت‬
‫وفيات االجنة بسبب عيوب خلقية او حاالت‬
‫اجهاض متكررة او وجود مواليد لديهن‬
‫بعض االعاقات او الخلل في السمع او البصر‬
‫او النطق او تأخر في التحصيل العلمي‪.‬‬
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‫أقارب من الدرجة األولى (اإلخوة واألخوات ‪ ،‬واآلباء ‪،‬‬
‫واألبناء)‬
‫أقارب من الدرجة الثانية (عم ‪ ،‬عمة ‪ ،‬جد ‪ ،‬ابن شقيق ‪،‬‬
‫بنت أخت)‬
‫أقارب من الدرجة الثالثة (ابناء العم)‬
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‫من هم المرضى المرشحين إلجراء استشارة وراثية؟‬
‫قصة شخصية أو عائلية لمرض وراثي‪.‬‬
‫تشوه خلقي‬
‫اضطراب صبغي‬
‫األمراض السرطانية التي تورث‬
‫قصة اسقاطين للحمل أو أكثر‬
‫والدة مولود متوفى‬
‫المرأة الحامل بعمر أكثر من ‪ 35‬سنة أو التي ترغب بالحمل بعد‬
‫هذا العمر‬
‫تحاليل دموية ترجح مشكلة وراثية أو صبغية‪.‬‬
‫بعض األمراض الوراثية لها ارتباط عرقي معين‬
‫األزواج ذوي القرابة (أبناء عموم أو خال ‪...‬الخ‬
Why Genetic Counselling is
Recommended
Counselling is recommend for any
of the following reasons:
1- A couple plans to start a family
and one of them or a close relative
has an inherited illness.
2- A parent already has one child
with a severe birth defect.
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Not all children who have birth defects have genetic
problems.
Sometimes, birth defects are caused by exposure to
a toxin (poison), infection, or physical trauma before
birth. Often, the cause of a birth defect isn't known.
Even if a child does have a genetic problem, there's
always a chance that it wasn't inherited and that it
happened because of some spontaneous error in the
child's cells, not the parents' cells.
3- A woman has had two or more
miscarriages.
Severe chromosome problems in the
fetus can sometimes lead to a
spontaneous miscarriage.
Several miscarriages may point to a
genetic problem.
4- A woman has delivered a stillborn
child with physical signs of a genetic
illness.
Many serious genetic illnesses cause
specific physical abnormalities that give
an affected child a very distinctive
appearance.
5- The pregnant woman is over age
34.
Chances of having a child with a chromosomal
problem (such as trisomy) increase when a
pregnant woman is older. Older fathers are at
risk to have children with new dominant genetic
mutations (those caused by a single genetic
defect that hasn't run in the family before).
6- A standard prenatal screening
test had an abnormal result.
If a screening test indicates a possible
genetic problem, genetic testing may be
recommended
7- A child has medical problems that
might be genetic.
When a child has medical problems
involving more than one body system,
genetic testing may be recommended to
identify the cause and make a diagnosis.
8- A child has medical problems that
are recognized as a specific genetic
syndrome.
Genetic testing is performed to confirm the
diagnosis. In some cases, it also might aid in
identifying the specific type or severity of a
genetic illness, which can help identify the most
appropriate treatment.
Steps in Genetic Counseling
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Genetic counseling generally involves
six steps:
Family and medical history assessment.
Analysis of genetic information (e.g.,
family history, genetic test results).
Communication of genetic
risk information.
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Education about inheritance, genetic testing,
management, risk reduction, resources and
research opportunities.
Supportive counseling to facilitate informed
choices and adaptation to the risk or
condition.
Follow up. This may include a written
summary, provision of referrals, and/or
subsequent genetic counseling session(s).
Factors increasing Risk
Maternal Age
 Paternal Age
 Ethnicity
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Family history considerations
Maternal Age
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Women over the age of 35
Slightly increased risk for chromosome
condition
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Down syndrome- extra #21
Trisomy 13 and 18- extra 13 & 18 severe
Sex chromosome conditions
Paternal Age
increased risk for:
 achondroplasia
 Marfan
 Noonan
‫ الحيوانات‬aneuploidy ‫الدراسات تشير إلى زيادة وتيرة في‬
‫المنوية في العقود السادس والسابع‬
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Genetic Disorder
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Chromosomal disorder
Single-gene disorder
Mitochondrial genetic disorder
Multifactorial disorder
Somatic cell genetic disorder
Single-gene disorder
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Autosomal dominant: Achondroplasia; Marfan
syndrome
Autosomal recessive: Albinism; Cystic fibrosis;
PKU
X-linked dominant: Hypophosphatemic
X-linked recessive: DMD; Hemophilia; G6PD
deficiency
Y-linked: Haired ears
Triplet repeats: Fragile X syndrome; Myotonic
dystrophy
Mitochondrial: Leber’s hereditary optic
neuropathy (LHON), MERRF
syndrome (Myoclonic Epilepsy with Ragged
Red Fibers). MELAS
“Mitochondrial encephalomyopathy, lactic
AR
AD
XR
XD
Y- Linked
Mitochondrial inheritance
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‫األمراض المتعددة األسباب‬
‫مرض السكر‪ ,‬وارتفاع ضغط الدم ‪,‬والربو‪ ,‬و الظهر‬
‫المشقوق(الصلب المشقوق)‪ ,‬و الشفة األرنبية‬
Genetic Testing During Pregnancy
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Amniocentesis:
- test usually performed between weeks 15 and 20 of
a woman's pregnancy.
- a small amount of amniotic fluid from around the
developing fetus is taken.
- This fluid can be tested to check for genetic
problems and to determine the sex of the child,
Chromosomes, Enzymes, AFP- protein
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Chorionic villus sampling (CVS):
performed between the 10th and 12th
weeks of pregnancy.
The doctor removes a small piece of
the placenta to check for genetic
problems in the fetus.
This can be tested to check
Chromosomes, Enzymes, DNA
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Ultrasound
This can be tested to check Fetal
Anatomy
PCR
FISH technique
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Fluorescence in situ hybridization (FISH) is
used to visualize and map the genetic
material in an individual's cells, including
specifc genes or portions of genes.
This is important for understanding a variety
of chromosomal abnormalities and other
genetic mutations.
FISH technique
chromosomal t (9;22)
PGD “Preimplantation genetic
diagnosis”
Gene therapy
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Gene therapy carries the promise of
cures for many diseases and for types
of medical treatment that didn't seem
possible until recently. With its potential
to eliminate and prevent hereditary
diseases such as cystic fibrosis and
hemophilia and its use as a possible
cure for heart disease, AIDS,
and cancer
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gene therapy is a potential medical miracle-worker.
But what about gene therapy for children? There's a
fair amount of risk involved, so thus far only seriously
ill kids or those with illnesses that can't be cured by
standard medical treatments have been involved in
clinical trials using gene therapy.
As those studies continue, gene therapy may soon
offer hope for children with serious illnesses that
don't respond to conventional therapies.
About Newborn Screening
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Testing every newborn for certain harmful
disorders at birth.
Many of these are metabolic
disorders "inborn errors of metabolism")
that interfere with the body's use of nutrients
to maintain healthy tissues and produce
energy.
Other disorders that screening can detect
include problems with hormones or the blood.
What are common genetic
disorders?
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Cystic fibrosis – Cystic fibrosis is tested
by examining 32 different mutations in
a particular gene. The disorder affects
the normal movement of salt in and out
of cells that line the lungs and
pancreas. This produces a thick, sticky
mucus which leads to frequent lung
infections.
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Down syndrome – Down syndrome is the
most common genetic birth defect, often
resulting in multiple abnormalities. It is
caused by an extra chromosome and results
in some degree of mental retardation, heart
defects and problems with vision and hearing.
Down syndrome is tested for by taking a
blood sample and performing a chromosome
analysis.
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Neurofibromatosis I –
Neurofibromatosis I is caused by
mutations in the NF1 gene. This gene
makes a protein called neurofibromin,
which is responsible for keeping cells
from growing and dividing rapidly.
Mutations in the NF1 gene cause
tumors to form on nerves throughout
the body.
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Sickle cell disease – Sickle cell disease
is caused by a red blood cell disorder.
Hemoglobin electrophoresis, a test that
measures the different types of
hemoglobin in the blood, is used to
diagnose the disease.
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Tay-Sachs disease – Tay-Sachs disease
is caused by the absence of a vital
enzyme called hexosaminidase-A (HexA). Without Hex-A, a fatty substance
builds up in cells, especially in the
brain’s nerve cells. This ongoing buildup
causes progressive cell damage. Tests
for the disease measure the amount of
Hex-A in the blood or in white blood
cells.