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CJD
A guide for patients and carers
What causes CJD?
As explained in the earlier section (What are the different types of CJD?), most cases of CJD are of unknown cause (sporadic). It may also be inherited (genetic or familial) or accidentally acquired, through medical or surgical equipment or treatment (iatrogenic) or possibly by eating infected meat products (variant). As explained in the earlier section (What is CJD?), changes in prion protein normally found in the brain are central to CJD.
Sporadic CJD
Sporadic CJD is of unknown cause, but it may be due to a spontaneous change in normal prion protein or the gene for this, which is called PRNP, in brain cells. If so, the disease is a ‘random’ biochemical event without any specific external cause.
Genetic or familial CJD
Genetic CJD is due to an abnormality (mutation) of the PRNP gene (see What are the different types of CJD?) which is responsible for producing normal prion protein. More than 30 different mutations have been found in different people with genetic CJD, and which of these an individual inherits seems to determine various factors of their disease, such as the age at which they develop symptoms and how their symptoms progress.
Occasionally, despite there being no apparent family history, a person may be found to have inherited CJD. It is therefore potentially important to undertake genetic testing in all cases of CJD. However the choice of whether or not to undertake genetic testing rests with the family (see Is there a genetic test for CJD?).
Iatrogenic CJD
Iatrogenic CJD is the result of the accidental transmission of disease from someone with CJD via medical or surgical treatment. Most cases occurred following the use of human growth hormone to treat short children. Between 1958 and 1985, thousands of children were treated worldwide with hormone extracted from the pituitary glands (at the base of the brain) of human corpses. A tiny minority subsequently developed CJD, and it is now known that this hormone supply included some from people who carried CJD infectivity. Growth hormone has not been obtained in this way in the UK or USA since 1985 and is now artificially manufactured, which rules out this risk.
A small number of people were infected following the use of dura mater repair material in certain neurosurgical and orthopaedic operations.
Other routes of infection, but causing only a handful of cases worldwide, include direct contact with brain or related tissue, such as corneal (eye surface) transplant or cross-infection from surgical instruments used on the brains of people with CJD. However, processes of organ donation and Department of Health guidelines for the re-use of surgical equipment have been tightened to reduce any such risks.
Awareness of the risk and routes of transmission of iatrogenic CJD now mean that it is a very unlikely cause of CJD. However, the incubation time (between infection and development of the disease) for CJD acquired from growth hormone may be unusually long. While most experts think it will not be more than 15-20 years, it is possible that more cases will occur.That acquired through corneal transplant or brain surgery probably develops within about four years of exposure.
Variant CJD
Variant CJD is thought to have been transmitted from cattle with BSE, via diet. Scientific analysis has shown that the same strain of prion agent causes human variant CJD and cattle BSE.There is no absolute proof of the involvement of diet, but this is overwhelmingly the most likely route of infection.
As explained in the following section, it is difficult to say how many people may develop variant CJD. While meat is no longer prepared in ways that might allow infection, it could take as long as 30 years for the disease to develop after the meat is eaten.
Sporadic CJD is of unknown cause, but it may be due to a spontaneous change in normal prion protein or the gene for this, which is called PRNP, in brain cells. If so, the disease is a ‘random’ biochemical event without any specific external cause.
Genetic or familial CJD
Genetic CJD is due to an abnormality (mutation) of the PRNP gene (see What are the different types of CJD?) which is responsible for producing normal prion protein. More than 30 different mutations have been found in different people with genetic CJD, and which of these an individual inherits seems to determine various factors of their disease, such as the age at which they develop symptoms and how their symptoms progress.
Occasionally, despite there being no apparent family history, a person may be found to have inherited CJD. It is therefore potentially important to undertake genetic testing in all cases of CJD. However the choice of whether or not to undertake genetic testing rests with the family (see Is there a genetic test for CJD?).
Iatrogenic CJD
Iatrogenic CJD is the result of the accidental transmission of disease from someone with CJD via medical or surgical treatment. Most cases occurred following the use of human growth hormone to treat short children. Between 1958 and 1985, thousands of children were treated worldwide with hormone extracted from the pituitary glands (at the base of the brain) of human corpses. A tiny minority subsequently developed CJD, and it is now known that this hormone supply included some from people who carried CJD infectivity. Growth hormone has not been obtained in this way in the UK or USA since 1985 and is now artificially manufactured, which rules out this risk.
A small number of people were infected following the use of dura mater repair material in certain neurosurgical and orthopaedic operations.
Other routes of infection, but causing only a handful of cases worldwide, include direct contact with brain or related tissue, such as corneal (eye surface) transplant or cross-infection from surgical instruments used on the brains of people with CJD. However, processes of organ donation and Department of Health guidelines for the re-use of surgical equipment have been tightened to reduce any such risks.
Awareness of the risk and routes of transmission of iatrogenic CJD now mean that it is a very unlikely cause of CJD. However, the incubation time (between infection and development of the disease) for CJD acquired from growth hormone may be unusually long. While most experts think it will not be more than 15-20 years, it is possible that more cases will occur.That acquired through corneal transplant or brain surgery probably develops within about four years of exposure.
Variant CJD
Variant CJD is thought to have been transmitted from cattle with BSE, via diet. Scientific analysis has shown that the same strain of prion agent causes human variant CJD and cattle BSE.There is no absolute proof of the involvement of diet, but this is overwhelmingly the most likely route of infection.
As explained in the following section, it is difficult to say how many people may develop variant CJD. While meat is no longer prepared in ways that might allow infection, it could take as long as 30 years for the disease to develop after the meat is eaten.
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Contents
- Introduction
- What is CJD?
- What are the different types of CJD?
- What precautions do I need to take to stop CJD spreading?
- Can I get CJD from eating meat?
- How does the brain of someone with CJD differ from normal?
- What causes CJD?
- What does "genetic susceptibility" to CJD mean?
- Is there a genetic test for CJD?
- Can CJD be avoided, and is it catching?
- What are the symptoms of CJD, and how does the disease progress?
- How is CJD diagnosed?
- Are other conditions easily mistaken for CJD?
- How is CJD treated?
- What impact can CJD have on families of poepl with the condition?
- What support is available for carers of people with CJD?
- Conclusion
- Organisations that may be able to help
