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Human prion diseases 

Human prion diseases

Human prion diseases

R G Will



Number of cases of iatrogenic CJD worldwide updated.

Number of cases of vCJD worldwide updated.

Diagnostic criteria for sporadic CJD updated to include MRI brain scan.

Updated on 28 Nov 2012. The previous version of this content can be found here.
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date: 23 April 2017

Prion protein (for proteinacious infectious particle) is a membrane-associated glycoprotein present in all mammalian species. Its normal function is unknown, but in prion diseases (also known as transmissible spongiform encephalopathies) a post-translationally modified form of the protein, partially resistant to protease digestion, is deposited in the brain and associated—after long incubation periods—with neuronal dysfunction and death.

Particular prion diseases

Creutzfeldt–Jakob disease (CJD)—several forms are recognized: (1) Sporadic—a rare condition typically presenting in late middle age with a rapidly progressive dementia associated with a range of neurological signs, most commonly myoclonus of the limbs, cerebellar ataxia and rigidity. Few patients survive for more than 2 years. (2) Hereditary—dominant pattern of inheritance; age at death is typically 5 to 10 years younger than in sporadic disease. (3) Iatrogenic—exposures in or adjacent to the nervous system (e.g. neurosurgical instruments, dura mater grafts, corneal transplants) typically present in a similar manner to sporadic disease; peripheral exposure to infection (pituitary hormones) usually manifests with progressive cerebellar ataxia. (4) Variant—bovine spongiform encephalopathy (BSE) was identified in 1986 as a prion disease in cattle, with the favoured hypothesis being that contamination of feed, probably with tissues from the central nervous system of affected animals. Variant CJD is caused by transmission of BSE to humans. Typical presentation is with psychiatric symptoms, followed after a period of months by progressive ataxia, dementia, and choreiform or dystonic involuntary movements which often evolve into myoclonus. It is likely that the maximum number of cases will be no more than a few hundred, with the mean age at death being 30 years.

Kuru—in Papua New Guinea this disease was transmitted in the course of ritual cannibalism, which ceased by 1960, hence there have been no cases in people born after 1959. Typical presentation was with headache and limb pain, progressing to a cerebellar syndrome, with eventual immobility.

Investigation, treatment, and prevention

Investigation—there is no test for the presence of the infectious agent, hence diagnosis depends on the recognition of clinical characteristics, sometimes supported by (1) electroencephalography—periodic triphasic complexes are seen in 60 to 70% of cases of sporadic CJD and in some cases of iatrogenic CJD; (2) cerebrospinal fluid analysis—elevation of 14-3-3 protein in the cerebrospinal fluid is about 90% sensitive and specific for sporadic CJD, but less useful for variant CJD; (3) MRI—with appropriate imaging protocols, localized abnormalities may be seen in the caudate nucleus and putamen in sporadic CJD, and the pulvinar region of the posterior thalamus in variant CJD; (4) tissue biopsy of brain or tonsil.

Treatment and prevention—there is nothing that influences the clinical course of human prion diseases, nor any treatment to prevent the development of neurological disease after infection.

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