medical genetics lecture 5 genetic counseling. objectives 1.to understand the principle steps of...
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Medical Genetics
LECTURE 5Genetic Counseling
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Objectives
1. To understand the principle steps of genetic counseling.
2. To know the ethical principles in performing genetic counseling.
3. To understand unique features of genetic counseling in Arabic/Islamic communities.
4. To know the sequence of steps for pre-marital screening.
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Genetic Counselling
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• Genetic disorders:• Chromosomal• Single gene• Multifactorial• Mitochondrial• Acquired somatic
• Only single disorders follow a clearly defined pedigree pattern of inheritance “Mendelian Pattern”.
• During genetic counselling it is essential to establish whether or not the disorder is Mendelian and to calculate the precise risk of recurrence.
Genetic Counselling for Mendelian Disorders
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• Pattern of transmission judged from family tree. For several diseases the family tree may be
conclusive even if accurate diagnosis is not made.
• For some diseases pedigree pattern is not helpful and only clinical diagnosis is used
• For some disorders the pattern looks complicated and the exact diagnosis cannot be made.
• More common, a combination of clinical diagnosis and comparable pedigree pattern is required.
Establishment of Mendelian Inheritance
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Essential Components of Genetic Counselling
Essential Components of Genetic Counselling
History and pedigree
construction
Clinical Examination
Confirmatorydiagnosis
Counselling
Availableoptions
Calculation ofrecurrence risk
Follow-up
- History findings- Clinical examination findings- Radiology findings- Laboratory parameter results- DNA studies results- Others
Recurrence Risk
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ETHICAL PRINCIPLESETHICAL
PRINCIPLES
BeneficenceBeneficence
AutonomyAutonomy
JusticeJustice Non-MaleficenceNon-Maleficence
VeracityVeracity
FidelityFidelityالمنفعة
اإلستقاللية
العدالة اإليذاء و الضرر عدم
اإلخالص
الصحة و الصدق
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Genetic Counseling in Achondroplasia
• It is inherited in an AD manner.
• Homozygous achondroplasia is a lethal condition.
• > 80% of achondroplasia cases have parents with normal stature i.e.: de novo (new) gene mutation.
• Such parents have a low risk of having another child with achondroplasia.
• Prenatal molecular genetic testing is available.
Reem Sallam, MD, PhD
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Genetic counseling - case
• An individual with achondroplasia who has a reproductive partner with normal stature has a 50% risk in each pregnancy of having a child with achondroplasia.
Achondroplasia (Heterozygous)Normal stature (Homozygous)
Child w/ achondroplasia. Child w/ normal stature
Reem Sallam, MD, PhD
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Genetic counseling - caseWhen both parents have achondroplasia,
the risk to their offspring of having normal stature is 25%; of having achondroplasia, 50%; and of having homozygous achondroplasia (a lethal condition), 25%.
Achondroplasia (Heterozygous)Normal stature (Homozygous)
Child w/ achondroplasia.
Child w/ normal statureHomozygous achondroplasia
Reem Sallam, MD, PhD
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Arabic/Islamic Communities
Unique featuresStrong Religious believes
Combined family Living style
Strong link to traditions and
customs
High rate of Consanguineous
marriages
Possibility of polygamy
Large family size
ReligiousAnd cultural
cohesionSpecial views on
Reproductive issues
Familyplanning
Abortion(IVF) In-vitrofertilization
AdoptionArtificial
inseminationFetalrights
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Premarital Screening*Man -History
-(Physical Examination) BloodSample
Genetic Screening (Laboratory)
Carrier affected Normal
No Problem from marriage from
any Women
Safe Marriage
**Women –History -(Physical examination)
BloodSample
Genetic Screening (Laboratory)
Carrier affected NormalNo Problem from
marriage from any man
Safe Marriage
Genetic Counseling(advise no marriage with carrier or affected)
Not safe Marriage
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Good Luck
Reem Sallam, MD, PhD