"Degenerative" Genetic Diseases Flashcards
What is the name for skills that include self-control, memory, self-monitoring, organization, control of emotions, starting and completing tasks, etc. (tasks of daily living)?
executive function
What is it called when someone is using too many words to describe something when fewer would suffice?
circumlocution
What may be an indicator of reduced function in Alzheimer’s disease?
circumlocution
What is a mutation that arises where there is no family history of the condition (may be a new genetic variant in a family)?
De novo mutation
What is the most common cause of dementia in the elderly?
Alzheimer’s
Alzheimer’s is typically diagnosed over what age in those affected?
65
What does Alzheimer’s disease result in?
progressive memory loss and premature death
Alzheimer’s has a ___% mortality per year after diagnosis
10
Once diagnosed with advanced dementia, half of the AD patients die within?
6 months
Although Alzheimer’s is not a specific cause of death, it increases their vulnerability to what?
illness and infection due to:
-injuries from falls
-poor nutrition or dehydration
-aspiration pneumonia due to inherent swallowing difficulties
What is the main common cause of death in Alzheimer’s disease patients?
aspiration pneumonia
What are the hallmark pathologic changes of Alzheimer’s Disease?
- amyloid plaques
- neurofibrillary tangles
What are abnormal deposits of the protein beta amyloid in the space between neurons?
amyloid plaques
What is formed by clumps of tau protein, which is part of the structure of the microtubules that support the structure of the neuron (limit communication between neurons)?
neurofibrillary tangles
Amyloid plaques and neurofibrillary tangles result in what?
-synaptic connections between neurons are lost and many neurons stop functioning and die
-atrophy of the brain occurs
-functioning and memory processes greatly decrease
What are the manifestations of Alzheimer’s disease?
- memory deficits
- language changes
- visuospatial skills
- neurobehavioral effects
What are the memory deficits associated with AD?
- recent: unable to remember many events after AD onset
- remote: able to remember some events that occurred prior to AD onset
What are the language changes associated with AD?
- verbal disfluency and circumlocution
- anomia (forgetting words)
- reduced vocabulary
- diminished comprehension
What are the visuospatial skills associated with AD disease?
- misplaced items
- get lost frequently
What are the neurobehavioral effects associated with AD?
- loss of or fragmented sleep
- depression and/or psychosis
- loss of executive function
What are the two different types of AD?
- early-onset
- late-onset
Early-onset AD usually occurs between what ages?
30-60, but can occur as young as 20
What percentage of AD cases are related to early-onset genes?
1-5%
Early-onset AD is commonly associated with what inheritance pattern?
autosomal dominant
What are the genes associated with early-onset Alzheimer’s disease?
- amyloid precursor protein gene (APP)
- presenilin 1 (PSEN1)
- presenilin 2 (PSEN2)
Which early-onset AD gene has over 30 mutations associated with early-onset AD and may be involved in early neural development, but exact function is unknown?
amyloid precursor protein gene (APP)
Which early-onset AD gene has over 150 million mutations and can lead to an overproduction of a longer and more toxic beta amyloid peptide and plaque formation?
presenilin 1 (PSEN1)
Which early-onset AD gene is the rarest of the three mutations and has an unknown mechanism but perhaps increases apoptosis in neurodegeneration?
presenilin 2 (PSEN2)
What chromosome is the APP gene located on?
chromosome 21
Individuals with Down Syndrome have trisomy 21 and an increased expression of what?
the APP protein
What increases the development of neurofibrillary tangles and beta amyloid plaques?
down syndrome
Individuals with down syndrome have a higher risk of what?
early-onset AD
What is the average lifespan of an individual with Down Syndrome?
60 years
Late-onset AD typically occurs after the age of what?
65
What percentage of cases of AD are late-onset?
over 95%
Genetics of late-onset AD represents what types of influences?
genetic and environmental influences
How many genes have been identified that are associated with late-onset AD?
20
What is the most firmly identified gene involved in late-onset AD?
apolipoprotein E (APOE)
What does the APOE variant allele also increase the risk of?
other forms of dementia (including vascular dementia and Lewy Body dementia)
What are the risks for late-onset AD in order?
- age
- family history of affected (1st degree relative)
- presence of APOE polymorphism
The APOE allele exists in 3 forms, what are they?
- APOE epsilon 2
- APOE epsilon 3
- APOE epsilon 4
Which APOE allele is the least common allele, is found in 5-10% of population, and appears to reduce the risk of late-onset AD?
APOE epsilon 2
Which APOE allele is the most common allele, is found in 70-80% of population, and plays a neutral role in risk of late-onset AD?
APOE epsilon 3
Which APOE allele is found in 10-15% of population, and appears to increase the risk for AD and is associated with an earlier onset?
APOE epsilon 4
What increases risk 3 to 8-fold, depending on whether a person has one or two copies?
APOE epsilon 4
APOE is a susceptibility gene, not a what?
determinant gene
Having 1-2 copies of APOE epsilon 4 does not mean what?
that AD will develop in 100% of cases
What is considered a non-reversible, progressive neurodegenerative disease?
Huntington’s Disease
What occurs primarily in Caucasian people of NW European ancestry and most commonly begins in mid-life but can begin earlier or later?
Huntington’s Disease
Onset of Huntington’s Disease before the age of 20 is considered what?
juvenile HD
What is the inheritance pattern of Huntington’s disease?
autosomal dominant
Affected individuals with HD are considered what?
heterozygous
What are some of the neuromuscular coordination manifestations of Huntington’s disease?
- chorea
- gait abnormalities
- absence of smooth eye movement
What are rapid, involuntary movements of the face, trunk, and limbs?
chorea
What are the psychosocial and behavioral manifestations of Huntington’s disease?
- irritability, anxiety, depression, disrupted social relationships, paranoia, aggression, delusions
- loss of insight, inflexibility, memory loss, impaired judgement
What gene codes for the protein called Huntington?
HTT
The mutated form of the HTT gene in HD consists of an expanded what?
CAG trinucleotide repeat
What is the codon for glutamine?
CAG
The average non-affected individual has how many CAG repeats?
17-20
A higher number of CAG repeats correlates to what in HD?
earlier onset and greater severity of disease
If inheritance of HTT allele in Huntington’s is from the father, what happens?
patients tend to develop disease early by about 3 years (paternal allele is more likely to have more CAG repeats than maternal allele)
In HD genetic testing, less than 35 CAG repeats is considered what type of result?
negative test result, so no chance of developing Huntington’s
In HD genetic testing, 36-39 CAG repeats is considered what type of result?
uninformative test result, so an individual may or may not develop HD but they are at a risk for it; their children are also at risk due to CAG repeat instability across generations
In HD genetic testing, more than 40 CAG repeats is considered what type of result?
positive test result, so they will always develop HD
Due to the instability of the CAG gene in HD, you may have a family that this arises _____
de novo
What is the most common lethal inherited disorder among Caucasians in the US?
cystic fibrosis
Cystic fibrosis is more common in persons of what descent?
Northern European descent
What is the inheritance pattern of Cystic fibrosis?
autosomal recessive