Week 5 lecture 2- huntington's disease

Question 1

Huntington disease

Answer 1

Neurodegenerative disease
Type of chorea
Chronic, progressive, hereditary disease
Usually of adult onset
Fits criteria for mendelian autosomal dominant inheritance

Question 1

Symptoms of huntingtons

Answer 1

excessive, spontaneous, irregular movements (chorea)
other motor disorders (rigidity)

Question 2

Autosomal dominant inheritance criteria

Answer 2

• Equal incidences in both sexes
• Equal transmission by both sexes
• 50% of the offspring of an HD parent will become affected if they live long enough
• Offspring who do not develop HD by old age will not pass on HD to their descendants
• Also borderline cases where someone carries an intermediate allele

Question 3

General characteristics of HD

Answer 3

• Commonly equal in men and women
• Mean age of onset: 35-44yrs
• Diagnosis is usually 8-10yrs after onset
• Onset takes place before 20 in 5-10% of cases and can occur as early as 4yrs of age (Juvenile HD)
• Death usually occurs around 50-60yrs
• Survival length after onset is about 13-17yrs
• In about 20% of cases onset is after 50yrs and can happen as late as 84yrs
• Very late onset cases often present with chorea only and relatively little other disability
  o These patients may remain reasonably intellectually intact and with minimal motor disability until death
• Can be divided into 3 clinical stages- Each stage lasts about 5yrs

Question 4

Symptoms of juvenile HD

Answer 4

o Rigidity
o Hypokinesia
o Seizures
o Chronic movements

Question 5

Neuropathology of HD

Answer 5

Generalized shrinkage of the brain
Preferential atrophy of the caudate nucleus and putamen (in the corpus striatum)

Question 6

Differences between HD and PD

Answer 6

• Primary motor disorder in PD is tremor
  o Chorea in HD
• HD inevitably progresses to a severe dementia
  o Only 10-15% of PD patients become demented
• Executive deficits found in both are more marked and more debilitating in early HD than in PD
• Cognitive impairment generally more severe at all stages of HD
• Environmental factors are likely to be causative of PD
  o HD is caused by autosomal dominant inheritance
• In PD drug and surgical treatments allow sufferers to enjoy a reasonable lifestyle, despite the progression of their disease. Research on a cure or slowing of the disease progression is well advanced
  o Drug treatments for symptoms of HD are less effective. A cure for HD appears to be a long way off