Lecture 19. Genetic Counseling
What do genetic counselors do? - answer-Interpret family history other information
-Patient education
-Counsel to promote informed choice and adaptation (to disease or risk thereof
Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) - answer-autosomal
dominant
-Average age of presentation is 31 years, but presentation is highly variable
-
Limitations of Genetic Testing for ARVC - answer-~50% of patients tested will have
detectable mutation
-Negative result does not rule out ARVD/C
Significance of many gene variants is unknown
-Not all genes for ARVD/C are known
-Genetic testing is unable to determine who will actually develop ARVD/C, when they
will develop it, or how severe it might be
Translational Medicine - answerthe medium between What can we learn from gene
testing and What are people telling us they need
Screening Tests - answer-During pregnancy
-For early signs of cancer
-Newborn screening
-Sensitivity/False positive rate?
Genetic Diagnostic Tests - answer-Before or after symptoms develop?
-Genome-wide, or specific genes?
-How well do we understand the range of normal variation in the genes we look at?
-Can we predict the severity of a condition based on genotype?
-Genetic heterogeneity?
Risk Prediction - answer-Decision-making BASED on genetic/genomic information.
-ACTION! PLANNING! Reproductive, surgical, financial, emotional.
Casual Explanation - answer-Understanding, control
closure, acceptance
-ACTION? Sometimes, nothing
Reasons for Prenatal Genetic Counseling Referral - answer-Maternal Age
-Previous Child with a Chromosome Abn.
-Parental Chromosome Rearrangement
, -Previous Child with neural tube defect
-Ethnicity/Carrier screening
-Single gene disorders
-Abnormal maternal serum screening -results
-Abnormal Ultrasound
-Teratogens
-Infertility
-Baseline risk of some birth defect for ANY pregnancy is 3-4% regardless
Prenatal SCREENING - answer-Goal is to identify of those apparently healthy
pregnancies that are at increased risk of a specific disorder to justify invasive prenatal
testing (CVS or amniocentesis)
-First trimester screening = nuchal translucency + PAPP-A + hCG + nasal bone (Down
syndrome, T18, T13)
-Second trimester screening (triple or quad screen) Down syndrome & T18
MS-AFP screening for neural tube defects
Prenatal DIAGNOSIS - answer-Chorionic Villus Sampling (CVS)
-Amniocentesis (Karyotype, FISH, prenatal microarray)
-1/150-1/300 risk of miscarriage
Nuchal Translucency - answer-An abnormal fluid collection behind the fetal neck has
been strongly associated with aneuploidy. This nuchal translucency NT has been
reported as a late first-trimester finding identified between 10-14 weeks gestation.
-the detection rate jump to 95% if you use the patented test
Carrier Screening - answer-identify couples at risk of having a child with a disease
-challenges:
allellic heterogeneity, therefore could be deemed a non-carrier but still have the residual
risk of being a carrier
Pre-Implantation Genetic Diagnosis (PGD) - answerused to test the embryo prior to
implantation in vitro fertilization
Cell-Free Fetal DNA in Maternal Blood - answer-in Maternal Blood
- placental dandruff -> cells shed into mother
-poss non-invasive screen test in the future
-might last in body after pregnancy
-some conditions have more shedding (pre-eclampsia)
Tumor suppressors, oncogenes, and DNA mismatch repair - answer-genes in the body
that prevent cancer from occurring, since cancer is genetic
sporadic cancers - answer-mutations occur in a single somatic cell which divides and
developed into a tumor
What do genetic counselors do? - answer-Interpret family history other information
-Patient education
-Counsel to promote informed choice and adaptation (to disease or risk thereof
Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) - answer-autosomal
dominant
-Average age of presentation is 31 years, but presentation is highly variable
-
Limitations of Genetic Testing for ARVC - answer-~50% of patients tested will have
detectable mutation
-Negative result does not rule out ARVD/C
Significance of many gene variants is unknown
-Not all genes for ARVD/C are known
-Genetic testing is unable to determine who will actually develop ARVD/C, when they
will develop it, or how severe it might be
Translational Medicine - answerthe medium between What can we learn from gene
testing and What are people telling us they need
Screening Tests - answer-During pregnancy
-For early signs of cancer
-Newborn screening
-Sensitivity/False positive rate?
Genetic Diagnostic Tests - answer-Before or after symptoms develop?
-Genome-wide, or specific genes?
-How well do we understand the range of normal variation in the genes we look at?
-Can we predict the severity of a condition based on genotype?
-Genetic heterogeneity?
Risk Prediction - answer-Decision-making BASED on genetic/genomic information.
-ACTION! PLANNING! Reproductive, surgical, financial, emotional.
Casual Explanation - answer-Understanding, control
closure, acceptance
-ACTION? Sometimes, nothing
Reasons for Prenatal Genetic Counseling Referral - answer-Maternal Age
-Previous Child with a Chromosome Abn.
-Parental Chromosome Rearrangement
, -Previous Child with neural tube defect
-Ethnicity/Carrier screening
-Single gene disorders
-Abnormal maternal serum screening -results
-Abnormal Ultrasound
-Teratogens
-Infertility
-Baseline risk of some birth defect for ANY pregnancy is 3-4% regardless
Prenatal SCREENING - answer-Goal is to identify of those apparently healthy
pregnancies that are at increased risk of a specific disorder to justify invasive prenatal
testing (CVS or amniocentesis)
-First trimester screening = nuchal translucency + PAPP-A + hCG + nasal bone (Down
syndrome, T18, T13)
-Second trimester screening (triple or quad screen) Down syndrome & T18
MS-AFP screening for neural tube defects
Prenatal DIAGNOSIS - answer-Chorionic Villus Sampling (CVS)
-Amniocentesis (Karyotype, FISH, prenatal microarray)
-1/150-1/300 risk of miscarriage
Nuchal Translucency - answer-An abnormal fluid collection behind the fetal neck has
been strongly associated with aneuploidy. This nuchal translucency NT has been
reported as a late first-trimester finding identified between 10-14 weeks gestation.
-the detection rate jump to 95% if you use the patented test
Carrier Screening - answer-identify couples at risk of having a child with a disease
-challenges:
allellic heterogeneity, therefore could be deemed a non-carrier but still have the residual
risk of being a carrier
Pre-Implantation Genetic Diagnosis (PGD) - answerused to test the embryo prior to
implantation in vitro fertilization
Cell-Free Fetal DNA in Maternal Blood - answer-in Maternal Blood
- placental dandruff -> cells shed into mother
-poss non-invasive screen test in the future
-might last in body after pregnancy
-some conditions have more shedding (pre-eclampsia)
Tumor suppressors, oncogenes, and DNA mismatch repair - answer-genes in the body
that prevent cancer from occurring, since cancer is genetic
sporadic cancers - answer-mutations occur in a single somatic cell which divides and
developed into a tumor
