Objectives of Genetic Counselling

Genetic counselling can come up in the context of obstetrics, paediatrics and adult medicine. For example, during antenatal screening, paediatric community clinic or any adult specialty.

The objective of genetic counselling is to not only 'break bad news' about the condition to the patient or parent but to answer any questions they have about it. "Will they lead a normal life?" is a high priority question in the back of their minds. Since the context is genetics, another question will be "Will I pass this on to my children and grandchildren?"

This leads to why the following are hot topics in genetic counselling;

  • Carrier status - Am I affected or passing this on? How likely will my child get it?
  • Penetrance - if my child gets the condition, how likely is it they will suffer from it?
  • Fertility - In fact will I even be able to have children of my own? If I can, what are the options if I don't want to pass it on?
  • Long term prognosis - Will I be affected immediately or later? Will this cut my life span? Will I be going in and out of hospital a lot? Can I stay normal?

Step by step counselling

1. Regarding the patient

  • Establish who is at the consultation (partner? family member? friend?)
  • Why are they here (or why they think they are here)?
  • How much do they know so far?

 

2. Regarding the consultation

  • Clarifying what you know about what the patient already knows or thinks
  • Establish what the consultation will be about --- constructing a family tree/genogram if not done already, explaining what the genetic condition in mind is (including the inheritance pattern), patient options (screening, management, fertility), possibility of notifying other family members to come for testing.

 

3. Construct the family tree

  • Establish the age each family member was diagnosed with the condition.
  • Ask how they were primarily affected because some conditions (ie Stickler Syndrome) could manifest only some signs within the family, guiding the clinician as to which gene mutation it could be.
  • Like any history, ask about the patient's in concern past medical and surgical history. Depending on which condition you have in mind, it is worth asking about the pregnancy, paediatric history as well as current complaints.

 

4. The genetic condition

  • Explain what the condition is - how it affects most patients.
  • Explain inheritance patterns.
  • You could potentially discuss what they may expect in terms of future ailments or reproductive effects, life span etc. However, this depends how ready the patient / family are to receive further information as such. Be guided by how much they want to know.

 

5. Patient options

If this is a first consultation, establish whether the patient would like genetic testing or not - not everyone wants to know!

Once the diagnosis has been made, in most genetic consultations, families are more than satisfied with the relief that comes with a diagnosis (at last!). In some consults, it does not end there.

  • Take the opportunity to empower the family or patient with knowledge in terms of what to expect in the future... and what kind of multi-disciplinarian involvement there might be.
  • For some cases (i.e. cancer genetics consultations) you can offer patients screening options to minimize future risks.
  • If this is a patient who seeks to start or continue a family, discuss fertility options and whether they would want prenatal testing as well as what they would do if the test is positive.

 

6. Family members

If the patient has been diagnosed with a condition or confirmed a carrier, it may be of benefit for other family members to step forward for genetic testing as well. Do not assume that the patient will always want other family members to know. Genetic testing is a very sensitive subject.

Some patients are happy for the clinician to contact family members or tell them themselves to have testing done. Others may be more reluctant for various cultural or social reasons (i.e. arranged marriage prospects, disclosure of information to insurance companies or employers).

Drawing a pedigree / genogram

  1. Explain that you are about to draw a family tree and you might ask some sensitive questions (but reassure them that these are questions are standard in every history).
  2. Always start with the proband. Remember to ask their age and write down the ages of each relative if possible. Whenever you record partners: check if they are related to each other and how (i.e. consanguinity).
  3. Ask about brothers or sisters - are they all from the same mother and father? Are they adopted?
  4. Ask about their mother's side and father's side separately, again checking if they are all from the same mother (proband's grandmother) or father (proband's grandfather).
  5. Ask about children - with current partner, previous partners, miscarriages, terminated pregnancies.
  6. NOW check - who has been affected with the condition in concern. Who knows their carrier status.
  7. And if possible, any other family history of illnesses.

Further detail on drawing pedigrees can be found in the paediatrics skills section on Fastbleep.

An example of a genogram

Genogram / genetic tree

Scenarios to think about

CHROMOSOMAL

(Down's (trisomy 21), Turner's (45, X0), Klinefelter's (XXY))

What kind of chromosomal abnormality is it? The wrong number of one type of chromosome (i.e. trisomies), the wrong number of an entire set of chromosomes (i.e. triploidy), the wrong shape (i.e. ring), the wrong sequence (i.e. inversion) or... A portion of the chromosome has been deleted or duplicated.

Once that has been established, the next question is how it happened in the first place. Is it due to a translocation? A non-disjunction during cell division? Germline mosaicism?

 

AUTOSOMAL DOMINANT

Penetrance --- the likelihood someone with the gene mutation will or will not express it in their phenotype. It could be age-dependent, complete or incomplete. In age-dependent penetrance, you are more likely to show signs and symptoms as you age (e.g. Huntington's Disease). In incomplete penetrance, not all people with the genotype will suffer with the phenotype (e.g. Brugada Syndrome).

Mosaicism --- Can be somatic or germline. If somatic - this is a new mutation during early embryogenesis so the phenotype is expressed only partially (e.g. cutaneous features of Neurofibromatosis type I in one dermatome only). If germline - a mutation present only in gonadal cells therefore the parent is unaffected but the offspring are.

Anticipation --- When the disease becomes increasingly severe with every generation. (ie Huntington's Disease)

 

AUTOSOMAL RECESSIVE

(e.g. Cystic Fibrosis, Sickle Cell Disease)

Consanguinity --- When there are couplings between members within the same family autosomal recessive conditions become far more common.

Carrier Status --- When there is a known affected family member, the remaining question for unaffected relatives is whether they are carriers and could pass it on to their offspring.

     

X-LINKED DOMINANT

There are 2 types - X-linked dominant inheritance (e.g. Rett syndrome) and X-linked semi-dominant inheritance (e.g. X-linked Hereditary Motor and Sensory Neuropathy)

The male foetus seldom survives pregnancy in an X-linked dominant inheritance whereas in an X-linked semi-dominant inheritance, they may survive but the disorder is very severe. Therefore the question of how severely affected the patient will be is inevitable.

 

X-LINKED RECESSIVE

(e.g. Duchenne Muscular Dystrophy)

A typical family tree will show a history of unaffected carrier mothers giving way to affected sons and either unaffected or carrier daughters... and if the affected son lives to a reproductive age, he would have unaffected sons and carrier daughters.

However it is not as simple as it sounds for the carrier daughter. Whether she manifests features of the phenotype depends on whether she has unfavourable skewing of X-inactivation. The girl inherits 2 X chromosomes where one of them can become inactivated. If the X chromosome carrying the mutation is inactivated, the girl remains unaffected. However if the other X chromosome is inactivated, she will become affected.

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