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YEAR 5: Microbiology and Infection > MI: Prion Disease > Flashcards

MI: Prion Disease Flashcards

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1
Q

What is the rapid plasma reagent test?

A

Test for active syphilis

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2
Q

Name a marker of rapid neurodegeneration.

A

14-3-3

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3
Q

What is a characteristic finding of CJD on a diffusion-weight MRI?

A

Increased signal in the cortex of the right parietal lobe

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4
Q

What does ‘prion’ stand for?

A

Protein-only infectious agent

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5
Q

What are prion diseases?

A
  • Rare transmissble spongiform encephalopathies caused by prions
  • They lead to spongiform vacuolisation of the brain and rapid neurodegeneration
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6
Q

On which chromosome is the normal prion gene found?

A

20

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7
Q

What is a possible physiological role of the normal prion protein?

A

It may have some role in copper metabolism

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8
Q

On which codon are the three polymorphisms of prion proteins found?

What are the three polymorphisms?

A
  • Codon 129
  • MM (predisposes to prion diseases)
  • MV
  • VV

NOTE: M = methionine, V = valine

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9
Q

Describe the structure of the normal prion protein.

A

Alpha-helix

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10
Q

Describe the structure of an abnormal prion protein.

A

Beta-pleated sheet

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11
Q

Why is the abnormal prion protein difficult to get rid of?

A

Resistant to proteases and radiation

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12
Q

How does prion replication take place?

A

Seeding of an abnormal prion protein (PrPsc) seems to act as a template which promotes the conversion of PrP to the insoluble PrPsc

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13
Q

List some sporadic and acquired types of prion disease.

A

Sporadic - CJD (mainly in older people)

Acquired:

  • Kuru
  • Variant CJD (results from BSE epidemic)
  • Iatrogenic CJD
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14
Q

Which gene mutation is associated with prion disease?

A

PRNP

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15
Q

Give some examples of inherited prion diseases.

A
  • Fatal familial insomnia
  • Gerstmann-Straussler-Sheinker syndrome
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16
Q

Describe the clinical features of sporadic CJD.

A
  • Rapid dementia
  • Myoclonus
  • Cortical blindness
  • Akinetic mutism
  • LMN signs
  • NOTE: usually in older people (>65)
17
Q

What are some possible causes of sporadic CJD?

A
  • Somatic PRNP mutation
  • Spontaneous conversion of PrP into PrPsc
  • Environmental exposure to prions
18
Q

Describe the EEG appearance in sporadic CJD.

A

Period, triphasic complexes

19
Q

Describe the MRI appearance of sporadic CJD.

A
  • Increased signal in the basal ganglia
  • Increased intensity on DWI MRI of the cortex and basal ganglia
20
Q

Which markers will be raised in the CSF of a patient with CJD?

A

14-3-3

S100

21
Q

What is the only way of confirming a diagnosis of CJD?

A

Brain biopsy (usually at autopsy)

22
Q

Describe the histological appearance of CJD.

A

Spongiform vacuolisation

NOTE: there are amyloid plaques but these are different from the plaques seen in Alzheimer’s disease

23
Q

List the differential diagnosis for CJD.

A
  • Alzheimer’s disease
  • Vascular dementia
  • CNS neoplasms
  • Cerebral vasculitis
  • Paraneoplastic syndromes
24
Q

What is variant CJD?

A

CJD in younger people that has resulted from the BSE epidemic

25
Q

Describe the clinical features of vCJD

A
  • Younger age of onset (20s)
  • Psychiatric onset (dysphoria, anxiety, delusions, hallucinations)
  • Followed by neurological symptoms (peripherap sensory symptoms, ataxia, myoclonus, chorea, dementia)
26
Q

What is a characteristic MRI feature of vCJD?

A

Pulvinar sign - high intensity in the putamen

27
Q

How is the use of CSF markers different in vCJD?

A

14-3-3 and S100 are NOT useful in vCJD

28
Q

Which investigation is most useful for vCJD?

A
  • Tonsillar biopsy - prions localise in lymphoid tissue

NOTE: this is not useful in CJD

29
Q

Describe the role of neurogenetics in vCJD.

A

Almost 100% of patients are MM at codon 129

30
Q

List some causes of iatrogenic CJD.

A
  • Human cadaveric growth hormone
  • Corneal transplants
  • Neurosurgical procedures
  • Blood transfusions
31
Q

Outline the clinical features of iatrogenic CJD.

A
  • Starts with progressive ataxia
  • Dementia and myoclonus occur at a later stage
32
Q

What is the inheritance pattern of inherited prion disease?

A

Autosomal dominant

33
Q

What are some alternative diagnoses for someone presenting with features suggestive of prion disease?

A
  • Spinocerebellar ataxia
  • Huntington’s disease
34
Q

Describe the clinical features of Gerstmann-Straussler-Sheinker syndrome.

A
  • Slowly progressive ataxia
  • Diminished reflexes
  • Dementia

NOTE: PRNP P102L mutation is most common

35
Q

Describe the clinical features of fatal familial insomnia.

A
  • Untreatable insomnia
  • Dysautonomia (blood pressure and heart rate dysregulation)
  • Ataxia
  • Thalamic degeneration

NOTE: PRNP D178N mutation is most common

36
Q

Outline the principles of treament of CJD.

A
  • Symptomatic - clonazepam for clonus
  • Delaying prion conversion - quinacrine, pentosan, tetracycline
  • Anti-prion antibody - blocks progression in mice but cannot access CNS
  • Depletion of neuronal cellular prion protein - blocks neuronal cell loss and reverses early spongiosis in mic
37
Q

Where should possible cases be reported to?

A
  • National prion clinic (Queen Square, UCL)
  • NCJDSU in Edinburgh

YEAR 5: Microbiology and Infection (24 decks)

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