What is it?
Creutzfeldt-Jakob disease is a prion disease. These are rare diseases characterized by degeneration of the central nervous system and are also known as subacute spongiform encephalopathies (TSEs). They are due to the accumulation in the brain of a normal but poorly conformed protein, the prion protein. Unfortunately, Creutzfeldt-Jakob disease is characterized by rapid and fatal progression and lack of treatment. There are 100 to 150 cases each year in France .
Symptoms of Creutzfeldt-Jakob disease
The disease often begins with non-specific disorders such as insomnia or anxiety. Gradually, disorders of memory, orientation and language are installed. It is then manifested by psychiatric disorders as well as cerebellar ataxia (instability while standing upright and during the walk which is accompanied by stumbling similar to that of drunkenness). There are also typical lesions in the central nervous system (florid plaques, amyloid deposits of PrPres surrounded by vacuoles).
Both sexes are affected, however, with a high frequency in young adults.
Unfortunately, there is no reliable diagnostic test. An electroencephalogram (EEG) can identify relatively specific disturbances of brain activity. MRI reveals particular abnormalities in certain regions of the brain (basal ganglia, cortex) for which differential diagnoses are few.
If all these clinical and paraclinical elements can make it possible to make a diagnosis of Creutzfeldt-Jakob disease, it is only a probability diagnosis: indeed, only the examination of the brain tissue, carried out on more often after death, allows affirming the diagnosis.
The origins of the disease
Creutzfeld-Jakob disease is the only human disease that can be genetically caused (due to a mutation in the gene coding for the prion protein, the E200K mutation being the most common), infectious cause (secondary to contamination) or of sporadic form (random occurrence, without mutation or exposure to an exogenous prion found).
However, the sporadic form is the most common: it represents 85% of all subacute transmissible spongiform encephalopathies (TSEs) diagnosed each year. In this case, the disease usually appears after 60 years and evolves over a period of about 6 months. When the disease is of genetic or infectious origin, the symptoms are earlier and evolve more slowly. In infectious forms, the incubation period can be extremely long and exceed 50 years.
Risk factors for Creutzfeldt-Jakob disease
Prion protein (PrPc) is a physiological protein found in a much conserved manner in many species. In neurons of the brain, the prion protein can become pathogenic by changing its three-dimensional conformation: it folds on itself very tightly, which makes it hydrophobic, poorly soluble and resistant to degradation. It is called prion protein “scrapie” (PrPsc). PRPs aggregate together and form deposits that multiply inside and outside brain cells, disrupting their function and survival mechanisms.
In this abnormal form, the prion protein is further capable of transmitting its conformational anomaly: in contact with a PrPsc, a normal prion protein in turn adopts an abnormal conformation. This is the domino effect.
The risk of transmission between individuals
Inter-individual transmission of prion diseases is possible in the case of tissue transplantation or following the administration of growth hormones. The highest risk tissues are from the central nervous system and the eye. To a lesser extent, cerebrospinal fluid, blood and certain organs (kidneys, lungs …) can also transmit the abnormal prion.
The risk of feeding
The transmission of a bovine prion to humans via the consumption of contaminated food is suspected in 1996, during the dramatic “mad cow” crisis. For several years, an outbreak of Bovine Spongiform Encephalopathy (BSE) has been reported in UK farms3. The spread of this prion disease, which affected several tens of thousands of animals each year, was probably due to the use of animal meal, produced from carcasses and insufficiently decontaminated. Its origin remains however discussed.
Prevention and treatment of Creutzfeldt-Jakob disease
Today, there is no specific treatment for prion diseases. The only medications that can be prescribed are those that can relieve or limit the different symptoms of the disease. Assistance for medico-social and psychological care is offered to patients and their families through the National Cell for the Management of CJD . The search for drugs to prevent the conversion of PrPc, promote the elimination of abnormal forms of protein and limit its spread is hopeful. An interesting target track PDK1, one of the cell mediators involved during the infection. Its inhibition would make it possible both to inhibit the conversion phenomenon by promoting the cleavage of PrPc, and to attenuate the consequences of its replication on the survival of the neurons.