Basics of Genetic Assessment and

Counseling

1 Dr Mohamed Fakhry

What is Genetic Counseling?

Communication processMedical education of affected individuals and the

general public concerning inherited disorder.Address individual concerns relating to development /

transmission of hereditary disorderGenetics counselors are health care professionals

with specialized graduate degrees and experience in medical genetics and counseling.

Consultant = individual who seeks genetic counseling

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When to see a Genetics Counselor

About 3% of babies are born with birth defects each year, according to the U.S. Centers for Disease Control and Prevention - and of the malformations that do occur, the most common are also among the most treatable.

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.

What Information should be provided?

Medical diagnosis and its effects in terms of prognosis and possible treatment

Mode of inheritance of disorder and the risk of developing and/or transmitting it

Choices or options available for dealing with the risks

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Steps in Genetic Counseling

Diagnosis : based on history, examination and investigations

Risk assessmentCommunicationDiscussion of OptionsLong-term contact and support

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Establishing the Diagnosis

Most crucial step in any genetic counselingIf incorrect - totally misleading information could be

given with tragic consequences

Reaching diagnosis involves three fundamental steps Taking a history Examination Undertaking appropriate investigations

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Information about consultand’s family is obtained by skilled genetics nurse or counselor

Pre-clinic telephone or home visit is helpfulClinic visit - full examinationAppropriate tests - chromosomes, molecular studies,

referral to specialists (neurology, ophthalmology)

Problems: Genetic heterogeneity, and Etiologic heterogeneity

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⇝Establishing the Diagnosis

TechniquesKaryotype Aminocentesis

Tests for abnormalities of chromosomes 1

TechniquesThis is a common test

used to determine the risk of a child having a genetics disorder that his ancestors were carriers for

Pedigree Analysis

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Genetic Genetic HeterogeneityHeterogeneity

def - disorder that can be caused by more than one genetic mechanism

Charcot-Marie-Tooth AD, AR, XR

Retinitis Pigmentosa AD, AR, XR

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Charcot-Marie-Tooth - also known as hereditary motor and sensory neuropathy type I (HMSN I) has been shown to result from a small duplication on short arm of chromosome 17

If found - this would aid in counseling

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⇝⇝Genetic Genetic HeterogeneityHeterogeneity

Etiologic Etiologic heterogeneityheterogeneity

Even though firm diagnosis - several causes may be possible

eg. Deafness and non-specific mental retardationEnvironmental or genetic factors

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Calculating and Presenting Calculating and Presenting the Riskthe Risk

Straightforward counseling situations - little more than knowledge about Mendelian inheritance is needed

Problems:Delayed age of onsetReduced penetranceUse of linked markers can make calculations more complex

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Presenting the Presenting the RiskRisk

Parents must be given as much background as possible

Recurrence risks should be quantified, qualified and placed in context

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QuantificatiQuantificationonMost prospective= future parents will have some

concept of risks

Experience demonstrates that some common misinterpretations occura risk of 1 in 4 may be remembered as 4 to 1, 1 in 40, or even 14% !!!

The risk only applies to every fourth child !!

It is ital to emphasize that the risk applies to each child, and that chance does not have a memory

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Discussing the Options

Provide consultants with all information needed to arrive at their own informed decision

Details of all the choices open to them - include a complete discussion of reproductive options

Alternative approaches to conception - AID, donor ova

Review of techniques, limitations and risks associated with methods available for prenatal diagnosis

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Communication and Communication and SupportSupport

Communication - two way processCounselor provides informationReceptive to fears and aspirations (hopes):

expressed or unexpressed by consultantInformation - present in clear, sympathetic and

appropriate manner

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Communication and Communication and SupportSupport

Individual or couple will be extremely upset (worried) when first aware of a genetic disorder

Complex psychological and emotional factors can influence counseling dialogue

Setting - agreeable, private and quiet, with more than enough time for discussion and questions

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CounseliCounselingng

Session can be so intense and insure that the amount and accuracy of information retained is not disappointing

Letter summarizing the topics discussed at counseling session is often sent to family

Follow-up home visit or clinic appointment to clarify any confusing issues

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Special Problems in Genetic Special Problems in Genetic CounselingCounseling

Consanguinity

Adoption= التبني and genetic disorders

Disputed Paternity

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Paternity TestingPaternity Testing

Genetic fingerprinting using minisatellite repeat sequence probes

Pattern of DNA fragments generated by those probes is so highly polymorphic that the restriction map is unique to each individual

Specific as fingerprints

21 Dr Mohamed Fakhry