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Prion diseases
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SPONGIFORM ENCEPHALOPATHIES


1. Human transmissible spongiform encephalopathies (including Creutzfeldt-Jakob (C-J) disease and kuru) have been transmitted to primates and to other animals through cell-free injections of infected brain tissue. Spongiform encephalopathies occur in several mammalian species. Scrapie affects sheep, and bovine spongiform encephalopathy occurs primarily in cows. Kuru, which affects humans, is associated with cannibalism in New Guinea natives. C-J syndrome and Gerstmann-Straussler-Schenker syndrome, which affect humans, appear to occur through both genetic and infectious routes, as known for scrapie.

The infectious agent has been characterized and is resistant to inactivation by ultraviolet radiation, formalin, heat and enzymes which denature nucleic acids. It can be inactivated (i.e. its infectivity destroyed) by proteases and other treatments that denature proteins.
The term "prion" was used to describe this small proteinaceous infectious particle. Abnormal forms of the prion protein (a ubiquitous protein of unknown function) cause these neurodegenerative diseases.
The disease occurs when the normal cellular prion protein undergoes a conformational change to the abnormal form. This may occur spontaneously at an extremely low rate or at a higher rate if there is a defect in the gene. The agent can "replicate" when the abnormal form crosses the path of the normal, cellular prion protein and the abnormal prion induces the normal form to adopt a similar abnormal form.


MORE INFORMATION: http://www.nmia.com/~mdibble/prion.html

OR http://www.kcc.com.msu.edu/CAI/Pathology/CNS_Infections_F/CNS_2a.html

General outline   
Synonyms    CJD Most frequent Human prion disease (Kuru, Gerstmann), Classical sporadic CJD, Iatrogenic CJD, Familial CJD, Variant CJD (affects younger people)

Symptoms    Classic form of CJD: initial neurological symptoms including ataxia, visual difficulty (optical ataxia), in addition a rapidly progressive dementia featuring memory, orientation, language, praxis impairment leading to severe impairment of activities of daily living. Variant CJD features psychiatric symptoms including withdrawal, mood swings preceding the occurrence of neurological symptoms, unsteadiness on the feet, coordination difficulty, later language and word finding difficulty. Eventually they become demented.
Course    Sporadic: 6 month to a year; Onset: 65-70
Variant: Onset - Average age 28, rare cases 16-78
Caregiver problems    Caregiver requires special and quick support, because the disease is extremely distressing; the support needs to be intensive, multidisciplinary and coordinated.

Epidemiology    1 / 1.000.000
Variant form: 120 cases in UK, 4 in France, 1 in Italy. 
Heredity    One form familial - mutation in prion protein
GSS: genetic also mutation in prion protein
Aetiology    An abnormally folded protein called prion protein is involved in the spreading of the neuro-degeneration. Mechanism of neuro-degeneration should be explained in the different variants of the disease. Mutation in the prion protein gene in familial forms.

Diagnostic procedures    Classic form: In the CSF proteins of neuronal origins are significantly elevated (14/3/3). Tau protein in the CSF is also dramatically increased. In part of the patients the EEG shows typical tri-phasic complexes. CT, MRI, and PET / SPECT are non-specific.
Variant form: Tonsil biopsy demonstrates presence of prions in the lymphatic system. MRI shows typical changes in the variant (which).

Treatment and rehabilitation    None so far 

Ongoing research / Clinical trials    Number of clinical trials in UK
Vaccination being examined as possible strategy
Available services    CJD Network
National CJD Surveillance Unit in Edinburgh
Special funding available for care and information in UK
Units: Prion Clinic, Paddington, London
National CJD Surveillance Unit in Rome
CJD Network in France
Also in Germany
Further reading   

8/01/05
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