Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Human Genetics Spring 2023 > Tay Sachs > Flashcards

Tay Sachs Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

What is a lysosome?

A

Organelle that degrades complex molecules within cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

True or false: most LSD are asymptomatic at birth

A

TRUE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the gene and mode of inheritance of Tay Sachs?

A

HEXA (AR)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the biological mechanism in Tay Sachs?

A

GM2 ganglioside accumulation primarily in CNS leads to neurodegeneration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the carrier freq of AJ for Tay Sachs?

A

~1/30

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Besides AJ what other groups are affected by Tay Sachs?

A

French Quebec, Amish, Cajun

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the genotype/phenotype correlation in Tay Sachs?

A

Two null = infantile
One null + one missense = subacute juvenile-onset
Two missense = milder late-onset

(lower level of enzyme the more severe the phenotype)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

When does ganglioside accretion occur?

A

As early as the 10th week of gestation
Continues through year 5 of life

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the Hex A activity in the infantile form of Tay Sachs (untreated)?

A

0-5%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the phenotype of the infantile form of Tay Sachs (untreated)?

A

Onset by 6 mos
Death 2-4 years
Neurodegeneration 3-6 months
No organomegaly
Cherry red spot in almost all patients

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the neurodegeneration in the infantile form of Tay Sachs (untreated)?

A

Loss of motor skills with progressive weakness
Decreased attentiveness with increased startle response
Progressive spasticity, seizures, loss of vision, swallowing, awareness, followed by death

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is a cherry red spot?

A

Small circular red spot in the center of the macula
Produced when ganglion cells are filled with lipid degenerate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the Hex A activity in the juvenile and adult form of Tay Sachs (untreated)?

A

5-15%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the phenotype of the juvenile and adult form of Tay Sachs (untreated)?

A

Progressive dystonia, spasticity, incoordination, ataxia
Speech and cog decline
Optic atrophy +/- cherry red spot
Psychosis, agitation, hallucinations, dementia
Death after 10-15 years (juvenile)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are possible cardio findings in Tay Sachs?

A

prolonged QT interval
nonspecific T wave changes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How many mutations account for 94% allele carrier detection rate in AJ?

A

~6 mutations:
3 null
G269S
2 pseudo-deficiency alleles

17
Q

What should you suspect if both Hex A and Hex B levels are low?

A

Sandhoff Disease

18
Q

What does Pseudodeficiency mean in Tay Sachs?

A

Pseudodeficiency refers to an in vitro phenomenon caused by specific HEXA variants that renders the enzyme unable to process the synthetic (but not the natural) GM2 substrates, and leads to false positive enzyme testing results.

19
Q

What do we know about non-Jewish individuals, HEX A enzyme-based testing, and pseudodeficiency allele?

A

About 35% of non-Jewish individuals identified as heterozygotes by HEX A enzyme-based testing are carriers of a pseudodeficiency allele.

20
Q

What is an important note when ordering biochemical carrier testing in a pregnant person?

A

Leukocyte testing (rather than serum testing) should be ordered for TSD carrier detection in women who are pregnant or using oral contraceptive medication.

21
Q

What are the brain MRI findings in Tay Sachs?

A

Atrophy of white matter demyelination

22
Q

How do you treat Tay Sachs?

A

No preventative therapy (BMT, ERT, SRT not effective)
AEs for seizures
Respiratory support
Supplemental nutrition

23
Q

What is a differential diagnosis of Tay Sachs?

A

Activator-deficient TSD 1 (GM2 gangliosidosis, AB variant) caused by variants in GM2A

Normal Hex A and Hex B levels

24
Q

What are the clinical features of Sandhoff Disease?

A

Progressive neurodegeneration
Starts at 6 months
Hyperacusis
Cherry red spot
Blindness
Hepatosplenomegaly
Skeletal abnormalities

Deficiency of both HEX A & HEX B enzyme activity

25
Q

What disorders have cherry red spots?

A

GM1 gangliosidosis
Sandhoff
Infantile Gaucher
Niemann Pick type A
Galactosalidosis
Tay Sachs

26
Q

What are differential diagnoses of late-onset Tay Sachs?

A

SMA
Friedreich’s Ataxia
ALS
Kuf’s Disease

27
Q

What are differential diagnoses for neuropsychiatric findings of late-onset Tay Sachs?

A

Hepatolenticular degeneration
Niemann Pick type C
cerebrotendenous xanthomatosus
CNL
Metachromatic leukodystrophy
X-linked adrenoleukodystrophy

28
Q

What are acquired disorders that mimic Tay Sachs?

A

Lead and heavy metal poisoning
Infectious and post-infectious meningoencephalitis
Subacute sclerosing panencephalitis
Hydrocephalus

Human Genetics Spring 2023 (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions