case study- prions group #17 william k. vincent sonia morales
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Case Study- Prions
Group #17
William K. Vincent
Sonia Morales
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Prion Structure:
http://www.prions.com/prions.jpg
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Prion Diseases
• Known collectively as spongiform encephalopathies.
• No nucleic acid genome.• Examples:
– Kuru– Scrapie– BSE (Bovine Spongiform Encephalopathy)– CJD (Creutzfeld-Jacob Disease)
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The Prion Hypothesis
• Ability to infect resides in the protein’s abnormal transformation
• Infectious agent is a specific structural form of a standard cell protein, PrPc.– In an unusual prion form, protein has
pathogenic properties.
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Case Study•70-year-old woman•Severe headaches, dull and apathetic•Memory loss, moments of confusion•Abnormal EEG•Coma-like state•Occasional spontaneous clonic twitching of the arms and legs•Myoclonic jerking response to a loud noise•Patient died of pneumonia
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Post Mortem Findings
• Died four months after onset.
• Astrocytic gliosis of the cerebral cortex with fibrils.
• Intracellular vacuolation throughout the cerebral cortex were seen microscopically.
• No swelling
• No inflammation
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Possible Viral Neurological Diagnosis• Encephalitis
– Symptoms include:
• Headaches• Confusion• Unsteady gait• Coma• Amnesia
– often caused by a viral infection – enteroviruses are most common, including poliovirus and
echovirus – Herpes simplex infection, varicella, measles, adenovirus,
rabies, Eastern Equine Encephalitis Virus, West Nile virus.
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Possible Viral Neurological Diagnosis Continued…
• Chronic meningitis – Symptoms:
• Severe headaches • Decrease in consciousness
– About 90% of cases of viral meningitis are caused by members of a group of viruses known as enteroviruses.
– Herpesviruses and the mumps virus can also cause viral meningitis.
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Other Diseases to Consider in Diagnosis
• Symptoms similar to other progressive neurological disorders, such as Alzheimer’s or Huntington’s disease.
• CJD causes unique changes in brain tissue which can be seen at autopsy.
• Cause more rapid deterioration of a person’s abilities than Alzheimer’s disease or most other types of dementia.
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Actual Diagnosis: Creutzfeld-Jacob Disease
• First concern is to rule out treatable forms of dementia such as encephalitis or chronic meningitis.
• Standard diagnostic tests will include– A spinal tap (14-3-3 protein)– Electroencephalogram (EEG) – Computerized tomography – Magnetic resonance imaging (MRI)
• The only way to confirm a diagnosis of CJD is by brain biopsy or autopsy.
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• Median age at death– 68 years (Classical)– 28 years (Variant)
• Median duration of illness– 4-5 months (Classical)– 13-14 months (Variant)
• Clinical signs and symptoms– Dementia; early neurologic signs (Classical)– Prominent psychiatric/behavioral symptoms; delayed
neurologic signs (Variant)
Clinical and Pathological Characteristics of CJD and its Variant form
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Clinical and Pathological Characteristics of CJD and its Variant form
• Periodic sharp waves on electroencephalogram– Often present (Classical)– Often absent (Variant)
• Immunohitochemical analysis of brain tissue– Variable accumulation (Classical)– Marked accumulation of protease-resistance prion
protein (Variant)
• Presence in lymphoid tissue– Not readily detected (Classical)– Readily detected (Variant)
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Possible Modes of Transmission• Sporadic
– Cases where no known risk factor,– Infection thought to be acquired by either of the following
two:
• Inherited– It is an autosomal and dominant trait.
• Iatrogenic– Acquired infection
• Diet
– Medical procedures• Surgery• Growth hormone• Corneal transplants
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Key Features of Post-Mortem Findings Characteristic of a Prion
• Neuronal vacuolation
• Spongiosis
• Neuronal death
• Explicit glial reactions
• Deposition, mainly in the brain and lymphoreticular tissues, of PrPSc.
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Prominent gliosis
Sponge-Like Lesions
Post-Mortem Findings
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What key features distinguish the unconventional prion diseases from more conventional neurological viral diseases?
• Conventional neurological diseases are very small, filterable agents that require host cells to grow.
• These unconventional agents are:– confined to the central nervous system– have long incubation periods– show progressive fatal course of disease– characteristically have vacuolization of
neurons.
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Differences In Disease Between Viruses and Prions
• Viruses– Has a cytopathological
effect
– Incubation period depends on virus
– Causes an immune response
– Causes inflammatory response
• Prions– No cytopathological
effects
– Long incubation period
– Does not cause an immune response.
– Does not cause an inflammatory response
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Precautions a Pathologist Should Take for Protection Against Infection
• Normal sterilization procedures such as cooking, washing, and boiling do not destroy prions.
• Wash hands and exposed skin before eating, drinking, or smoking.
• Cover cuts and abrasions with waterproof dressings.
• Wear surgical gloves when handling a patient's tissues and fluids or dressing the patient's wounds.
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Precautions Continued…• Avoid cutting or sticking themselves with
instruments contaminated by the blood or other tissues.
• Use face protection if there is a risk of splashing blood or cerebrospinal fluid.
• Soak instruments in undiluted chlorine bleach for an hour or more– then use an autoclave (pressure cooker) to sterilize
them in distilled water for at least one hour at 132 - 134 degrees Centigrade.
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Stay tuned for new information on Prions…
Thank you!
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References Belay, E. D. and Schonberger, L.B. The Public Health Impact of Prion Diseases.
Annu. Rev. Public Health. 26:191-212 (2005).
Creutzfeldt-Jakob Disease Foundation, Inc. 2006 <http://www.cjdfoundation.org>.
Department of Health and Human Services: Centers for Disease Control and Prevention. 13 April 2007. CJD (Creutzfeldt-Jakob Disease, Classic).
Retrieved November 24 2007. <http://www.cdc.gov/ncidod/dvrd/cjd/index.htm>.
Dimmock, N.J., Easton, A.J., and Leppard K. N. “Prion Diseases.” Introduction to Modern Virology. Blackwell Publishing. 2007: 401-415.
Glan Clwyd Hospital DGH NHS Trust. Retrieved November 26 2007. <http://www.banes-pct.nhs.uk/documents/Board_Papers/2004/May/Agenda %20item%2014%20-%20Appendix%202%20-%20Guidance%20-%20CJD%20%20 2004%20BANES%20PCT.htm>.
Medline Plus. 7 September 2006. Encephalitis. Retrieved November 28, 2007.
<http://www.nlm.nih.gov/medlineplus/ency/article/001415.htm#Definition>.
Narang, H. K. A Critical Review of Atypical Cerebellum-Type Creutzfeldt-Jakob Disease: Its Relationship to ``New Variant'' CJD and Bovine Spongiform Encephalopathy. Experimental Biology and Medicine 226:629-639 (2001).
National Institute of Neurological Disorders and Stroke. 19 November 2007. Creutzfeldt-Jakob Disease. Retrieved November 22, 2007. <http://www.ninds. nih.gov/disorders/cjd/cjd.htm>.