Genetics Counseling Flashcards by Alex Stein

Why should PTs know about genetics

PTs are integral members of the health care team
PTs are among first contacts for parents of children exhibiting poor mm tone and delayed motor development
Knowledge of genetics will help PTs manage and care for their patients more effectively

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Pt related benefits of genetics knowledge by PTs

Generation of appropriate and timely referrals
Provision of accurate info
Understanding terminology
Effective advocate for pts

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Will your pts ask about genetics? - What percentage of patients seen by PTs had a condition that had a genetic component

30%

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Will your pts ask about genetics? - What percent of PTs reported that they had discussed genetic component of their problems with the patient

68%

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Will your pts ask about genetics? - what percent of PTs provided counseling about genetic concerns to some of their clients

18%

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What do PTs need to know about genetics

Examine one’s competence of practice on a regular basis - identifying areas where info related to genetics would be beneficial
Understand the social and psych implications of genetic services
Know how and when to make a referral

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Reasons to consider a genetics consultation - pediatric

Abnormal newborn screening results
Presence of birth defects
Abnormalities in growth
Intellectual disability or developmental delay
Seizure disorder
Blindness or Deafness

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Reasons to consider a genetics consultation - Adult

Personal or family hx of hereditary CA
Development of degenerative diseases
Other adult onset genetic disease

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Reasons to consider genetics consultation - prenatal

Mother 35 or older
Abnormal screening test
Family hx
Exposure to teratogen
Mother has medical condition
3 or more losses
Consanguinity 
Ethnic predisposition

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What happens during a genetics consultation

Assessmnet of family med hx, information, and social support
Family med hx
Physical exam
Diagnosis based on physical exam or offer testing

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Beighton score

Test for hypermobility (5/9) - common in many genetic conditions

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Uses of genetic testing

Diagnostic
Presymptomatic 
Predictive/Predisposition
Carrier
Prenatal/Preimplantation 
Screening

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Diagnostic tests are used to

make or confirm the diagnosis of a genetic disease

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Predisposition tests

Tests for genes that predispose toward developing a particular disorder
Not everyone with the gene develops the disease
Ex: CA

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Presymptomatic testing

Used to test for a genetic disease before the onset of symptoms
Everyone with the gene will develop the disease if they live long enough
Ex: Huntington, ALS

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Carrier testing

Detect unaffected carriers of a single gene for a recessive disease or chromosome abnormality
Carriers do not have the disease but may be at risk to have an affected child if partner is also a carrier
Ex: CF, mm dystrophy

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Prenatal tests

Used to detect genetic disorders in the fetus before birth

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Preimplantation genetic diagnosis

In vitro fertilization

Embryonic cells removed at 8 cell stage

Preimplantation genetic diagnosis - can be tested for

Chromosome abnormalities

Single gene disorders as indicated by family history

Screening tests

Used to screen the general population for the possibility of genetic disease

Newborn screening includes

Sickle cell
PKU
Galactosemia
Maple syrup urine
Homocystinuria
Biotinidase deficiency
Congenital adrenal hyperplasia
Hypothyroidism
CF

Prenatal screening

US screening for fetal abnormalities
Maternal serum screening for neural tube defects and DS
Free fetal DNA from maternal blood

Three kinds of genetic tests

Cytogenetic
DNA
Metabolic

Microarray tests

Look for sub microscopic duplications or deletions of genetic material
Do not detect changes in genetic code
May detect changes of unknown significance
Looking at the blocks in town example

Modes of inheritance

``` Autosomal dominant Autosomal recessive X linked Multifactorial/Epigenetic Chromosomal Contigous gene ```

Autosomal dominant

If a parent has the condition the child has a 50% chance of getting it

Autosomal dominant - penetrance, expressivity, onset

Reduced penetrance (may skip a generation) Variable expressivity Late onset

Trinucleotide repeat disorders - caused by

Slippage of the DNA polymerase during replication | Ex: Huntington, fragile x mm dystrophy

Autosomal recessive inheritance

Both parents are carriers, 25% chance child will show disease

X linked are more likely to occur

More likely with one sex over the other

Multifactorial inheritance

Environmental trigger needed to express the mutation

Contiguous gene syndromes

Involve deletion or duplication of several genes | Found to be the cause of several syndromes with overlapping features

Imprinting

Genetic defects due to not receiving a copy of a gene from a particular parent

Imprinting may be due to

Depletion in the chromosome received from that parent | OR from uniparental disomy (getting both copies of a chromosome from the same parent)

Mitochondrial inheritance

Disorders caused by genes in the mitochondria Mitochondria packaged into tail of sperm and lost at time of fertilization so always passed through female Males or females can be affected

Reproductive options

``` Chance Prenatal diagnosis Preimplantation genetic diagnosis Sperm/egg donation Adoption Sperm sorting for x linked disorders ```

How is genetic testing helpful

Reduces morbidity and mortality through close surveillance of high risk individuals Eliminates need for extra surveillance Allows for targeted care specific to disorder Provides risk info

Can genetic testing be harmful

Psychological impact of knowing Possible insurance discrimination Family discord because other family members are at risk

CRISPR/Cas9

Enzyme that is bacterial based that has the possibility of changing a genome Would lead to changing genetic makeup as a way to cure disease

Case example - Referral for tall structure and pectus excavatum - tall with long arms and long fingers - MH lens dislocation

Marfans syndrome | Autosomal dominant

Case example - Marfans syndrome - PT implication

``` Need exercise but can't do contact sports 30-50% reduction in oxygen uptake Prone to CV complications Back pain from kyphosis Joint laxity ```

Case example - Referral for joint laxity and a lot of dislocations, velvety, stretchy skin, wide scars, 9/9 on Beighton

Ehlers Danlos Syndrome Different types - she has hypermobility type Typical autosomal dominant

Case example - Ehlers - PT implication

``` Managing joint pain Cardiac monitoring They have a lot of disability Might have hypotonia Non weight bearing strengthening Posture Stabilization ```