What are the symptoms of prion diseases?
There are many symptoms of prion disease. The main one is dementia, i.e. a rapid deterioration in cognitive functions such as memory and language, to which are added various neurological symptoms such as myoclonus (muscle twitching), problems with balance, vision and coordination of movement. The disease may begin with sleep disorders or anxiety before the symptoms of dementia appear.
Sporadic Creutzfeldt-Jakob disease (CJD)
The sporadic form of Creutzfeldt-Jakob disease (CJD) begins on average around the age of 65. The disease progresses very rapidly, causing death after an average of 6 months.
Genetic forms of prion disease
There are three hereditary forms of prion disease: genetic Creutzfeldt-Jakob disease, Gerstmann-Straussler-Scheinker syndrome (GSSS) and Fatal Familial Insomnia (FFI). All three are due to a different mutation in the same gene coding for the prion protein. The course of these forms varies widely, from a few months to several years.
Symptoms may vary significantly from those presented above. While the symptoms of genetic CJD are similar to those of the sporadic form, Gerstmann-Straussler-Scheinker syndrome is more likely to be characterised by damage to the cerebellum with symptoms of ataxia, while Fatal Familial Insomnia is primarily characterised by very severe and intractable sleep disorders, associated with disturbances of the vegetative system (day-night rhythm, sphincter disorders, cardio-respiratory disorders, etc.).
Acquired forms of prion disease
Acquired forms are perhaps the best known. In particular, the variant form of Creutzfeldt-Jakob disease. This form appeared in the United Kingdom in 1996. It is linked to the ingestion of bovine derivatives contaminated with an abnormal prion protein responsible for bovine spongiform encephalopathy. It is best known as “mad cow disease”. The variant form of CJD mainly affects young adults (around the age of 30) and begins with psychiatric symptoms such as anxiety or depression, before neurological signs and, later, dementia appear. It progresses slightly more slowly than the sporadic form, over about 18 months.
There are other acquired forms of prion disease, such as iatrogenic Creutzfeldt-Jakob disease, i.e. transmitted by accident during a therapeutic procedure. This form of the disease came to light mainly in the 1970s and 1980s, after corneal or dura mater transplants or treatment with growth hormone, which at the time was produced from the pituitary glands of deceased patients. The incubation period for this form of the disease is 10 to 15 years.
Research at the Paris Brain Institute
Stéphane Haïk, team leader at the Institut du Cerveau and also coordinator of the Centre national de référence des maladies à prions, is working to develop diagnostic tests to detect Creutzfeldt-Jakob disease. His team has participated in the development of a biological test capable of detecting the prion responsible for variant Creutzfeldt-Jakob disease (vCJD) in blood.
For more information: https://institutducerveau-icm.org/en/actualite/a-biological-test-to-detect-creutzfeldt-jakob-disease/