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Microbiology > Prion disease > Flashcards

Prion disease Flashcards

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Biology 101 flashcards
1
Q

What is a prion?

A

An infectious agent consisting only of protein, which can fold in multiple, structurally distinct ways, at least one of which is transmissible to other prion proteins, leading to disease that is similar to viral infection.

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2
Q

Which diseases are thought to be caused by prions?

A

The rare Transmissible Spongiform Encephalopathies (TES)

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3
Q

Which system is affected by all known prion diseases in mammals?

A

The nervous system: all affect the structure of the brain or other neural tissue, resulting in rapid neuro-degeneration. All are currently untreatable and universally fatal.

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4
Q

What is PrP?

A

Prion protein - the protein that prions are made of, which may occur in both infectious and non-infectious forms. Healthy form found throughout the body, even in healthy people and animals.PrP found in infectious material has a different structure and is resistant to proteases

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5
Q

What is PrP^C?

A

PrPC is a normal protein found on the membranes of cells. The C refers to ‘cellular’ PrP. Predominantly expressed in CNS

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6
Q

Which chromosome has the gene for PrPC?

A

20

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7
Q

What is PrP^SC?

A

The infectious isoform of PrP. Sc refers to ‘scrapie’, the prototypic prion disease, occurring in sheep.

Able to convert normal PrPC proteins into the infectious isoform by changing their conformation, or shape; this, in turn, alters the way the proteins interconnect. PrPSc always causes prion disease. PrPSc has a higher proportion of β-sheet structure in place of the normal α-helix structure.

Protease/radiation resistant.
Seed of PrPSc acts as template which promotes irreversible conversion of PrP to insoluble PrPSc

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8
Q

Is there currently a cure for prion disease?

A

Nope

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9
Q

Which 2 genetic mutations are associated with prion disease?

A

Codon 129 polymorphism

Specific PRNP mutations

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10
Q

Give 2 neuro-genetic differential conditions to consider

A

Huntington’s

Spinocerebellar ataxia

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11
Q

What treatment may be given for the symptomatic relief of myoclonus in CJD?

A

Clonazepam
Sodium valporate
Levetiracetam
Piracetam

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12
Q

What is myoclonus?

A

Irregular short duration jerk like episodes involving the somatic (skeletal) musculature

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13
Q

In CJD which treatments are used to delay prion “conversion”?

A

Quinacrine
Pentosan
Tetracycline

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14
Q

What are the 3 broad types of prion disease and what percentage does each make up?

A 
Sporadic CJD (sCJD) - 80%
Acquired CJD -
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15
Q

Which 3 prion diseases belong to the “acquired CJD” category?

A

vCJD (variant)
Iatrogenic
Kuru

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16
Q

List 4 inherited prion diseases/types of disease

A

Familial CJD
Gerstmann-Straussler-Scheinker syndrome (GSS)
Fatal familial insomnia (FFI)
Various atypical dementias

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17
Q

What are the EEG changes in sCJD?

A

Serial EEG shows periodic triphasic changes

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18
Q

What are the EEG changes in vCJD?

A

Non-specific slow waves

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19
Q

What are the MRI changes in sCJD?

A

Normal/highlighting basal ganglia

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20
Q

What are the MRI changes in vCJD?

A

Posterior thalamus highlighted on MRI-T” (pulvinar sign)

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21
Q

What are the MRI changes in inherited prion disease?

A

Sometimes high signal in basal ganglia

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22
Q

Which two types of prion disease give a high basal ganglia signal on MRI?

A

sCJD and inherited prion diseases

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23
Q

Which protein may show an elevated CSF level in prion disease?

A

14-3-3 protein

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24
Q

Which type of prion disease is most associated with an elevated 14-3-3 protein?

A

sCJD

25
Q

Is CSF 14-3-3 a good diagnostic test for CJD?

A

No, it’s not sensitive or specific

Only half of patients diagnosed with CJD have an elevated 14-3-3 protein. About 1/3 of patients who do have an elevated 14-3-3 protein are found to have a different neurological disease, not CJD

26
Q

What does CJD stand for?

A

Creutzfeldt-Jakob disease

27
Q

In which type of CJD are diagnostic mutations present on PNRP (prion-protein gene) analysis?

A

Inherited prion diseases

(PNRP mutations not usually seen in sporadic or acquired CJD, but certain polymorphisms are associated with increased susceptibility)

28
Q

Which PNRP (prion-protein gene) polymorphism is a recognised genetic marker for increased CJD susceptibility in Caucasions?

A

Codon 129 - homozygosity (MM or VV) associated with increased risk

29
Q

In which type of CJD are all cases homozygous MM at codon 129?

A

vCJD

in sCJD and iatrogenic cases, most are homozygous

30
Q

Which type of homozygosity is most commonly associated with CJD susceptibility, MM or VV?

A

MM

But VV also has higher susceptibility than heterozygous state.

31
Q

In sCJD and iatrogenic CJD, which types of PrP^SC are detected by Western blot?

A

Types 1-3

32
Q

In vCJD, which type of PrP^Sc protein is detected by Western Blot and from where is the sample taken?

A

Type 4t
From tonsillar biopsy
(100% sensitivity and specificity)

33
Q

Give 2 post-mortem findings in sCJD

A

Spongiform vacuolation

PrP amyloid plaques

34
Q

Give 2 post-mortem findings in vCJD

A

PrP^Sc detectable in CNS and lymphoreticular tissue

Florid plaques

35
Q

Describe the aetiology of sCJD

A

Somatic (ie not inherited) PRNP mutation
OR
Spontaneous conversion of PrP^c to Prp^Sc and subsequent seeding

36
Q

Describe the aetiology of vCJD

A

Exposure to bovine spongiform encephalopathy (BSE, “mad cow disease”)

37
Q

Describe the aetiology of iatrogenic CJD

A

Innoculation with human prions - commonly during surgery

38
Q

Describe the aetiology of kuru

A

Exposure to human prions through cannibalism

Papua New Guinea

39
Q

What is the inheritance type (ie dominant/recessive etc) of the inherited prion diseases Gerstmann-Straussler-Scheinker syndrome and fatal familial insomnia?

A

Autosomal dominant

40
Q

How many families in the world have fatal familial insomnia (FFI)?

A

40-50, with ~100 affected individuals

41
Q

List 5 clinical features of sCJD

A 
Rapid, progressive dementia
Myoclonus
Cortical blindness
Akinetic mutism
Lower motor neuron signs
42
Q

What is the mean age of onset of sCJD?

A

45-75 years

43
Q

What is the mean survival time of sCJD?

A

6-12 months of symptom onset

44
Q

How does the age of onset differ in vCJD (compared to sCJD)?

A

Younger - typically around 30 years

45
Q

What is the mean survival time of vCJD?

A

~14 months

46
Q

Which symptoms develop first in vCJD?

A

Psychiatric: anxiety, paranoia, hallucinations

47
Q

In vCJD, which group of symptoms follow the psychiatric symptoms?

A

Neurological: peripheral sensory symptoms, ataxia, myoclonus

48
Q

List 3 late stage symptoms of vCJD

A

Chorea
Ataxia
Dementia

49
Q

What determines the speed of progression of iatrogenic CJD?

A

Route of inoculation - fastest if introduced directly into CNS

50
Q

What is the first symptom of iatrogenic CJD?

A

Progressive ataxia

51
Q

Give 2 later stage symptoms of iatrogenic CJD

A

Dementia

Myoclonus

52
Q

How long is the incubation period of kuru?

A

~45 years

53
Q

How does kuru present and what is the survival time from presentation?

A 
Progressive cerebellar syndrome
3 stages: ambulant, sedentary, terminal
"Laughing sickness" - pathologic bursts of laughter
Late/absent dementia
Death within 2 years
54
Q

When was the kuru epidemic in PNG?

A

1950s/60s

55
Q

When does Gerstmann-Straussler-Scheinker (GSS) present and what is the mean survival from this point?

A

Develops between 20-60 years

~5 year survival

56
Q

What are the 2 stages of GSS?

A

Dysarthria
Cerebellar ataxia
Dementia

(Gradual progression)

57
Q

How does fatal familial insomnia (FFI) initially present?

A

Insomnia and paranoia

58
Q

How do the symptoms of FFI progress?

A

Hallucinations and weight loss, followed by a final mute period

59
Q

What is the mean survival time of FFI?

A

1-18 months after start of symptoms

Microbiology (27 decks)

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