Prion Diseases

Question 1

What are the characteristics of prion diseases?

Answer 1

Spongiform encephalopathy
Slow neurodegenerative disease
Caused b proteinaceous infectious particles (prions)
No vision or genome so do not elicit immune response
extremely resistant to heat, disinfectants and radiation
Can be sporadic, genetic or acquired
Long incubation period of about 30 years

Question 2

What are the prion properties?

Answer 2

Normal protein is PrPc
Normal protein is protease sensitive and alpha helical
Encoded by gene on chromosome 20
Defective protein is protease resistant
Defective protein change from alpha helical to beta sheet
Aggregates into amyloid rods

Question 3

what is the prion pathology?

Answer 3

Confined to theCNS
Long incubation period
Loss of muscle coordination (ataxia or difficulty walking)
Functional disorder of the cerebellum
Dementia and diminished intellect and poor judgment
Progressive insomnia

Question 4

What are the human prion diseases?

Answer 4

Kuru- acquired, eradicated fatal disease
CJD
Variant CJD
GSS-inherited
Fatal familial insomnia(inherited)
Sporadic fatal insomnia

Question 5

What are the characteristics of CJD?

Answer 5

Sporadic
Rare but worldwide-10% familial with a prion gene
Spontaneous mutation or inherited
Mean age of 68 years

Question 6

What are the characteristics of variant CJD?

Answer 6

Acquired from eating infected beef or medical transmission
Occurs in younger individuals but older than 14 year old
Shorter incubation period(6 years)
Rapid progression
Mean age 28 years

Question 7

What are the modes of transmission of the prion diseases?

Answer 7

Spread of variant CJD occurs during surgical procedures from tissue
From ingestion of contaminated meat
Vertical transmission in familial cases

Question 8

How is the diagnosis of prion diseases done?

Answer 8

Brain MRI can show amyloid in cerebellum
Prions accumulates in tonsils
Elevated levels of 14-3-3 or tau protein in CSF
Proteinase K resistant in tonsil biopsy by western blot