Genetic Testing and Counseling Flashcards
What is assortive mating?
Mating of people with the same phenotype resulting in more of the phenotype than expected
What is linguistic homogamy?
Mating between individuals that have the same language
What is the founder effect?
Common ancestor
Geographically or socially isolated
Mutated gene becomes more prevalent (AR)
What is a population bottleneck?
Reduction in population size
Enhanced effects of gene drift
If lots of people die, those genes will be lost
But the remaining genes will appear to increase greatly
What is balanced polymorphism?
A process of natural selection
Two alleles are maintained in stable equilibrium because the heterozygote is more fit than either of the normal or affected homozygotes
What does perinatal mean?
28 hours to 28 days of life
What are some known factors causing perinatal hearing loss?
Low birth weight
Time spent in NICU (longer the time the greater the risk)
Infections such as (sepsis, CMV, mumps, measles, rubella, and bacterial meningitis)
Use of ototoxic medication
Hypoxia (or prolonged use of oxygen)
What can help establish if the hearing loss was pre- or post-lingual?
Record of speech and language milestones
Can infants naturally coo and babble up to 6 months old?
Yes
Even babies with hearing loss
What may be an indication of vestibular dysfunction perinatally?
Poor motor development
What is the first thing you should ask when assessing someone with hearing loss?
Family history
Should all children with hearing loss undergo a complete physical examination?
Yes
To look for features associated with syndromic conditions
Should parents and siblings also be examined when a child is suspected to have a syndromic hearing loss?
Yes
To look for subtle signs
Can you complete a hearing test on young children?
No
You can do OAEs or ABRs instead
Should laboratory tests be ordered for every child with hearing loss?
No
It’s not cost effective or practical
When should laboratory tests be ordered for children?
When history, physical examination, and the age of the patient suggest it
What is the purpose of getting a laboratory test?
To exclude or confirm a specific suspected diagnosis
Are blood count tests helpful in establishing the cause of hearing loss?
No
Can a urine analysis be helpful?
Yes
Important for some conditions involving blood in the urine
Alport syndrome
Can congenital and acquired neonatal thyroid hormone deficiency result in profound intellectual disability often accompanied by deafness?
Yes
Early treatment can prevent severe hearing loss
Are the thyroid hormones in pendred usually normal?
Yes
What can an electrocardiogram tell us?
It calculates the QT interval
When is an electrocardiogram done?
If there is a family history of syncope or sudden infant death
May indicate JLNS
When are high-resolution CT scans of the temporal bones done?
When a child has progressive SNHL and craniofacial anomalies
Can a CT scan also determine if there is an EVA or a mondini malformation?
Yes
What can EVAs and mondini malformations be an indication of?
Pendreds syndrome
When should a renal ultrasound be performed?
When BOR is suspected
What is a screening?
Tests used to identify people with a high risk of having a specific genetic disorder
What is a diagnostic test?
Tests performed that confirm or exclude a known/suspected genetic disorder in an individual showing symptoms
Also can be performed prenatally in a fetus at-risk for a certain genetic conditions
What is a genetic evaluation?
Genetic tests are typically performed by a trained genetic technicians
Genetic testing, such as genomic sequencing
What does genetic testing involve?
A detailed clinical and family history
Comprehensive examination of patient and if necessary, parents and siblings by a physician
Why do they test for GJB2 and GJB6 first?
Because they are so common
What are the steps that go into diagnosing a child?
Newborn hearing screening
Confirmation of hearing loss (diagnostic ABR)
Obtaining a detailed family history
ENT, audiology, and genetic evaluation
Molecular testing for GJB2/GJB6 mutations – first step for genetic testing
If negative, follow up with
Cranial imaging studies (if EVA +ve, then test for Pendred genes)
Cardiac evaluation/EKG (rule out long QT interval)
Ophthalmologic evaluation
Guided molecular testing for hearing loss genes - OtoSCOPE
What is OtoSCOPE?
A genetic panel for hearing loss
Tests for 152 genes known to cause non-syndromic hearing loss, usher and pendred syndrome, and other HL-related phenotypes
Does OtoSCOPE also test for GJB2 and GJB6?
Yes
What is FISH?
Fluorescence in situ hybridization
What does FISH do?
It provides researchers with a way to visualize and map the genetic material in an individual’s cells, including specific genes or portions of genes
This test may be used for understanding a variety of chromosomal abnormalities and other genetic mutations
How do you test for mitochondrial mutations?
By taking a DNA sample
What areas can you take a DNA sample from?
Any tissue
Blood, skin, sweat, and hair
Who should be tested for mitochondrial mutations?
Families exhibiting matrilineal (maternal line) inheritance
Individuals from high-risk families
Individuals from high-risk ethnic groups
All infants admitted to neonatal intensive care units
What are things that you’re supposed to do when diagnosing a child with hearing loss?
Detailed family history
Consider genetic etiology
Rule out syndromic HL
DNA testing for GJB2/GJB6 genes
Temporal bone imaging
What are things that you’re not supposed to do when diagnosing a child with hearing loss?
Call it sporadic or environmental
Quote a negligible recurrence risk
Offer a molecular panel for HL at the outset
What are some clinical benefits to identifying genetic conditions?
Provide professionals with an ability to make an accurate diagnosis and prognosis
Provide scientific explanations of why the problem occurred, and therefore, preventing/removing the blame game
Recognition of the risk of associated structural anomalies (e.g., congenital heart defects)
Recognition of the risk of associated developmental handicaps (e.g., learning & intellectual disability)
Provide accurate recurrence risk for off springs
Is it important to realize the limitations of genetic testing?
Yes
It may be used to rule out a specific disorder but may not identify the cause of a genetic disorder
Does genetic testing provide information about a person’s family members as well?
Yes
This is unique from other medical tests
What is misassigned paternity?
Dad may not be biological dad
This knowledge can generate complex problems
What is insurance discrimination?
Fear of genetic insurance discrimination may be a factor affecting decisions for genetic testing
Insurance companies have been known used genetic test results to deny coverage to individuals
What is GINA?
Genetic Information Nondiscrimination Act
Became law in 2008
Prohibits U.S. insurance companies and employers from discriminating on the basis of information derived from genetic tests
What is one of the few instances the Deaf community accepts genetic testing?
With Ushers
They want to be prepared for both hearing and vision loss
Is pre-test counseling just as important as post-test counseling?
Yes
