Variant CJD (vCJD)
Human Prion Diseases
by André Delacourte and Clive Evers
vCJD is a recent form of Creutzfeldt-Jakob disease, which belongs to a group of rare and fatal brain disorders called prion diseases.
vCJD is almost certainly caused by exposure to Bovine Spongiform Encephalopathy (BSE) a prion found in cattle. In 1996 ten teenagers in the UK had been diagnosed with vCJD. This was unusual and alarming. Also the occurrence of an epidemic of prion disease, BSE, among UK cattle from 1986 was thought to be no coincidence.
Like all other prion disease, vCJD is caused by a highly unusual infective agent called a prion, which is an abnormal form of a protein called PrP. However vCJD differs from sporadic CJD, which is far more common, in several respects:
- The majority of cases reported have been in young people with average age of onset of symptoms being 28.
- The course of illness is longer than sporadic CJD, being typically around a year
- The symptoms at the outset are often more psychiatric than neurological
- When the brains of people with vCJD are examined at post mortem the characteristic spongiform change was seen under the microscope but additionally alongside florid plaques.
It is still not clear how the young people may have been exposed to BSE. However it is known that spinal cord form infected animals may have ended up in the mechanically recovered meat, used in the manufacture of sausages, meat pies and hamburgers.
An investigation into a cluster of cases of vCJD in Leicestershire published in March 2001 produced additional information. Here 4 out of the 5 people with vCJD may have been exposed to the BSE agent through the purchase and consumption of beef from a butcher’s shop where the meat could have been contaminated with brain tissue. Analysis of the exposure of cases to this practice suggests that the incubation period for the development of vCJD may be between 10 and 16 years.
Variant CJD, new variant CJD
Symptoms and course
The symptoms of vCJD differ from those of sporadic CJD. Initially there is typically anxiety, depression, withdrawal and behavioural changes.
The patient may be referred first to a psychiatrist, rather than a neurologist. It may be very difficult early on to determine that the illness is a neurological rather than a psychiatric one.
The patient may also report persistent pain and odd sensations in the face and limbs.
After several weeks or months more obvious neurological symptoms may begin including:
- unsteadiness in walking, sudden jerky movements
- Progressive dementia (loss of mental function and symptoms of memory loss)
- Eventually the patient typically loses the ability to move or speak and will need 24 hour nursing care.
Death occurs on average around one year after the onset of symptoms. Up to April 2003 there had been 134 definite or probable cases of vCJD dead and alive. In January 2003 statistical evidence emerged form the NCJDSU in Edinburgh that the epidemic of vCJD was no longer increasing at its previous rate. It may have or be reaching its peak. However this is still not certain.
Causes and risk factors
It is not yet known what the likely route of transmission in vCJD is. It may be that young people consume more of whatever foodstuffs carried the most infectivity or it may be that young people are just more susceptible to the transmission of CJD via BSE. There is the same genetic susceptibility as found in sporadic CJD. BSE contaminated foodstuffs were also fed to sheep, pigs and poultry so exposure through their consumption cannot be ruled out. It is not known how many other people will develop vCJD without knowing the probable route of exposure. However as the incubation period is still uncertain there could still be many more cases in the future.
Up to April 2003 there had been 134 definite or probable cases of vCJD dead and alive. In January 2003 statistical evidence emerged form the NCJDSU in Edinburgh that the epidemic of vCJD was no longer increasing at its previous rate. It may have or be reaching its peak. However this is still not certain.
Diagnostic procedures as described in the generic description.Also, a brain biopsy may be carried out to detect signs of spongiform change. It has been shown that infectivity can be detected in tonsil tissue in cases of vCJD so tonsil biopsy may be suggested. As with other forms of CJD at present a definite diagnosis is only possible by examining the brain during a post-mortem examination. The hallmarks of CJD, spongiform change and loss of neurons, are present but the most striking feature is the presence of so called florid plaques. These are deposits scattered throughout the brain, which are surrounded by spongiform change.
Care and treatment
There is no treatment at present for CJD. However, there are a number of drugs, which can relieve the symptoms and make the patient more comfortable.
These include valproate and Clonazepam for jerking movements. The patient and their carers will also need much help from social services and nursing services.
National CJD Surveillance Unit Western General Hospital Crewe Road, Edinburgh EH4 2XU Scotland www.cjd.ed.ac.uk
In addition to surveillance and research they can organise intensive support for the person with CJD and their family.
Human BSE Foundation A charity set up by and for people who have been affected by vCJD. www.hbsef.org firstname.lastname@example.org
CJD Support Network Gillian Turner Birchwood, Heath Top, Ashley Heath Market Drayton Shropshire, TF9 4QR England www.cjdsupport.net
Prion Clinic Department of Neurology St Mary’s Hospital, Praed St. London, W2 1NY United Kingdom
- CJD and prion disease: an introduction and explanation. Alzheimer’s Society CJD Support Network. December 1998.
- Will, RG et al A new variant of Creutzfeldt Jakob disease in the UK. Lancet 1996; 347; pp 921-925
- Douglas, MJ et al Patients with new variant CJD disease and their families:care and information needs. National CJD Surveillance Unit, Edinburgh, Feb 1999.
- Variant CJD:Alzheimer’s Society CJD Support Network. Information Sheet No 4. April 2001
Last Updated: vendredi 09 octobre 2009