Download - Genetic Counseling 1
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What is genetic counselling?
The process by which patients or relativesat risk of a disorder that may be
hereditary are advised of theconsequences of the disorder, theprobability of developing or transmitting
it, and of the ways in which this may beprevented, avoided or ameliorated
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Genetic counsellors Clinical Geneticists
Genetic Nurse Specialists
Genetic Associates (Science graduates) Counsellors in specific areas (Haemophilia etc)
Should all healthcare professionals be able tocommunicate genetic issues?
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Genetic Testing Identification of disease genotype in a family
Identification of a genetic disease in a family?
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Pre-symptomatic Testing Identification of a genotype before a phenotype
develops
HD trinucleotide expansion
Identification of a marker of a disease beforesymptoms develop
High cholesterol in hypercholesterolaemia
Renal cysts in adult polycystic kidney disease
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Is the disease worth testing for?
Can we predict the course of the disease?
Can we improve treatment?
Can we affect outcome?
Is termination of pregnancy justified?
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Do we have an appropriate
test? Has the genetic change been identified? In the condition?
In the family? Is the test accurate and reproducible?
Is there a lab that will perform the test?
GENETIC TESTING IS NOT AVAILABLEFOR MOST SINGLE GENE DISORDERS
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HD as a model for
Pre-symptomatic testing
Highly sensitive and specific diagnostic
test
Fully penetrant disease
Relatively consistent clinical course
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Pre-enrollment appointmentPre-symptomatic testing
protocol
Confirm diagnosis in affected relative
Draw up family tree
General discussion about HD
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Second Appointment
Why are you having the test now?
What are the benefits of a result positive
or negative?
Who else is likely to be affected by yourresult?
Check knowledge base
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Third Appointment
How have you coped with major lifechanges in the past?
How will you get the result?
Who will you share it with?
Blood taken at this appointment
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Results
A firm date for result is given when theblood is taken
Result given in clinic or at home
Contact arranged for 2-4 weeks and thennegotiated
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CADASILAutosomal dominant disease - mutations inNOTCH gene
Recurrent strokes and resulting disability
Migraine may occur 10 years before onset of strokes
Variable clinical course but penetrance nearlycomplete
Often associated with a characteristic MRI scan
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Letter to neurologist This 24 year old woman has been complaining of
headache for the past 2 years. The headaches areassociated with visual aura and vomiting. She is themain carer for her 52 year old wheelchair-boundmother.
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Neurology appointment Symptom history strongly suggestive of migraine
Family history - stroke in mother and maternal uncle
Could be CADASIL - MRI scan ordered to confirm
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Letter to geneticist This 24 year old lady has a strong family history of
stroke. Her mother is wheelchair-bound at 52 and heruncle died at 47. Apart from intermittent migraine sheis in good health.
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Genetic Clinic Appointment Family history suggestive of CADASIL
Migraine may be associated but also common in the
general population - not necessarily symptomatic ofCADASIL
Discussion of genetic testing (sample from mother tolook for mutation)
Pre-symptomatic protocol explained
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Discussion Is MRI a pre-symptomatic test in this situation?
Which approach is better?
Could you combine approaches?
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Why do we place so much more emphasis on genetesting compared with other clinical testing?
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Treatable v non-treatableWhat sort of protocol should we have for:
Huntingtons disease
Breast cancer Bowel cancer
Polyposis coli
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Hypercholesterolaemia (high
blood cholesterol levels) Some people have a dominantly inherited mutation
leading to high cholesterol
Some have a genetic susceptibility to high cholesterol
We can all have high cholesterol if we dont eat adecent diet.
Drug treatments are expensive
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Is Hypercholesterolaemia a genetic problem
or a social problem? Does genetic testing have a role?
Do you eat a good diet? If not, would genetic testing make you improve it?
Statins are a class of drug that improve outcome inall forms of hypercholesterolaemia Should they be available to everyone or just individuals
with LDL receptor mutations?
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Genetic susceptibilityWhat would you do if you were told that your risk of
developing diabetes was twice the population risk
Change diet?
Exercise?
Panic?
Nothing?
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Data Protection Confidentiality
Individual rights versus social responsibility
Who owns genetic information?
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Martin (DMD) 1. Martin was diagnosed at 2yrs with DMD following
investigation for developmental delay. A dystrophindeletion is demonstrated in both Martin and his
mother Sue. Sue has 2 younger sisters neither of whomis in a stable relationship. Her mother died in a caraccident and there is little contact with the extendedfamily.
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Martin (DMD) 2 Sue who has a history of depression feels very guilty
about being a carrier of DMD. Her husband phonesthe department to say that they wish no further
contact from genetics. He says Sue has told her sistersthat there is a genetic test available and they are notinterested but may make contact later.
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Martin (DMD)
CAROL
SUEMARTIN