Huntingtons

Question 1

what is the gene mutation in Huntington’s disease?

Answer 1

chromosome 4
mutated HTT gene and mutated hHtt protein

Question 2

what is the brain abnormality noticed in a person with Huntington disease?

Answer 2

atrophy of the basal ganglia but enlarged lateral ventricles

Question 3

what type of chromosomal inheritance pattern does Huntington’s follow?

Answer 3

Inherited (autosomal dominant) progressive neurogenerative disorder

passed from parent to child through a mutation of a gene on chromosome 4

Question 4

If a parent has Huntington’s disease what is the likely hood the child will inherit it?

Answer 4

Each child of a parent with HD has a 50% chance of inheriting the HD gene

If a child does not inherit the HD mutation, he/she will not develop the disease and cannot pass it on to future generations

When HD occurs without a family history, it is called sporadic HD

Question 5

what is the typical onset of Huntington’s disease?

Answer 5

typical onset is 30-40s

juvenile onset is before someone is 20 years old

Question 6

what is the lifespan for a individual after diagnosis?

Answer 6

10-25 years from symptom onset

Question 7

if a patient has 27-35 CAGs what could be inferred about their ability to have the disease?

Answer 7

intermediate alleles

0% likelihood of developing disease phenotype

Question 8

if a patient has 36-39 CAGs what could be inferred about their ability to have the disease?

Answer 8

reduced penetrance

higher likelihood of developing disease phenotype

Question 9

if a patient has 40-55 CAGs what could be inferred about their ability to have the disease?

Answer 9

Huntington’s disease

-100% likelihood of developing disease phenotype

Question 10

if a patient has > 56 CAGs what could be inferred about their ability to have the disease?

Answer 10

juvenile Huntington’s disease

probable early onset and severe progressive phenotypes

Question 11

what is the pathophysiology of Huntington’s disease? how does it differ from parkinson’s disease?

Answer 11

Huntington’s disease is direct > indirect
parkinson’s disease is direct < indirect

huntingion’s disease motor symptoms are Chora, rigidity, akinesia, dystonia, and muscle spasms due to an imbalance in GABA, glutamate, dopamine, adenosine, and acetylcholine

Question 12

how is a medical diagnosis of huntington’s made? what is the scale
used?

Answer 12

based on a confirmed family history or positive genetic test plus the onset of motor disturbance
motor disturbance is defined by the Unified HD Rating Scale (UHDRS) total motor score (TMS)

subtle motor, cognitive and psychiatric deficits can be identified before the onset of manifest disease…referred to as the pre-manifest stage of the disease

Question 13

what is the scoring of the Unified HD Rating Scale (UHDRS) total motor score (TMS)?

Answer 13

score ranges from 0 (no motor abnormalities suggestive of HD) to 4 (≥99% to be due to HD), with a score of 4 defining motor onset or ‘manifest’ HD

Question 14

what are the clinical phases of HD?

Answer 14

pre-manifest
peri-manifest
manifest