genetic counseling 1

7/31/2019 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

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