CJD / vCJD / Mad Cow Disease News.

Creutzfeldt-Jakob disease (CJD) is a rare and fatal condition that affects the brain. CJD causes brain damage that becomes worse over time. Most people with CJD die from an infection within a year of the initial symptoms - often because the immobility caused by CJD can make people with the condition vulnerable. There is no proven cure for any type of CJD, although clinical trials are investigating possible treatments. Treatment involves keeping the patient as comfortable as possible and reducing symptoms through medicine use.
Genetic CJD

Genetic CJD is a very rare illness. In this form, CJD is caused by an inherited abnormal gene. The illness is therefore not "caught" in any way and there is no causal relationship between this form and BSE. In most cases, the illness is known within the family because of the family history.

Occasionally, genetic cases are seen in which no previous family history is identified. The definitive test in relation to genetic CJD is a blood test in order that the gene can be analysed to see whether there is any genetic abnormality. The United Kingdom has a population of around 58 million and there are only a few deaths due to genetic CJD in a year.

Iatrogenic CJD

Iatrogenic CJD is also very rare. This is CJD which has been accidentally transmitted during the course of medical or surgical procedures. The most important example of this in the United Kingdom relates to CJD transmitted via Human Growth Hormone treatment in childhood. There are only a few deaths per year due to iatrogenic CJD in the United Kingdom. The diagnosis is usually clear from the history of a relevant medical or surgical treatment in the past.

Sporadic CJD

Sporadic CJD is numerically the most common form of CJD. It is not confined to the United Kingdom and, indeed, has been found in every country in the world where it has been looked for. In general, it affects about one person per million of the population. There are therefore some fifty to sixty deaths per year due to sporadic CJD in the United Kingdom. Similar figures are seen in other countries such as Australia, Canada and the USA.

The cause of sporadic CJD remains uncertain. However, the most favoured current theory suggests that the normal prion protein in the brain undergoes a spontaneous change to the abnormal form, thereby resulting in disease. If this theory is correct (and it has not been proven at this point) then the disease arises simply as a chance event inside the brain. On this basis, it would not be "caught" in any way.

Variant CJD

Variant CJD was first reported in 1996. At this point in time, the CJD Surveillance Unit has not seen any cases of variant CJD with symptoms that began before 1994. Aside from 6 cases in France, one case in Ireland, one case in Italy and one case in the USA, variant CJD has been confined to the United Kingdom. The current view on variant CJD is that it has resulted from transmission of infection from BSE in cattle to humans via infectivity in food.

We have had many enquiries to the relationship between sporadic CJD and variant CJD. Sporadic CJD is of unknown cause. However, detailed investigation over many years has failed to provide any evidence to suggest that it is related to diet. It was first described in 1921 and therefore predates the BSE epidemic by many years. Sporadic CJD is found in countries throughout the world regardless of the presence of BSE. There is therefore no evidence to suggest that sporadic CJD is in any way the result of BSE. On the other hand, the timing of the appearance of variant CJD and its geographical distribution in the world strongly suggested a connection with BSE in cattle. Laboratory scientific work has shown that the protein agent involved in sporadic CJD has quite different behavioural properties to that seen in the protein agent from variant CJD. In addition, the behaviour of the variant CJD agent is very like that of BSE. There is therefore scientific laboratory evidence to support the view that variant CJD and BSE are related, whereas sporadic CJD is not causally related either to BSE or variant CJD.

Sporadic CJD and variant CJD have certain clinical and pathological differences

The age of onset is generally different in variant and sporadic CJD. Variant CJD has tended to affect younger individuals with an average age of onset of around 27. Sporadic CJD has tended to affect middle-aged and elderly individuals. However, this difference is not absolute. There are those with variant CJD with a relatively older onset (including one case aged 74). Sporadic CJD may also affect very young individuals on occasions, including those in their teens and twenties. There is therefore a small overlap in the age group affected by variant CJD and sporadic CJD. The age of an individual is not an absolute guide to the type of CJD.

The duration of illness is generally different in variant CJD and sporadic CJD. Many cases of variant CJD have durations of a year or more. The duration of sporadic CJD is typically a few months, and, in a few cases, a few weeks. However, there is again no absolute distinction. There are cases of variant CJD who have died after an illness of only a few months and there are occasional cases of sporadic CJD with durations of one or two years or even longer. Therefore, the duration of illness is not an absolute guide to the form of CJD.

The symptoms of sporadic and variant CJD tend to be different. In particular, sporadic CJD tends to present with a clearly neurological illness that follows a very rapidly progressive course. In variant CJD, the initial presentation is often with psychiatric or behavioural symptoms and it may not be clear that the individual has neurological illness until several months after the onset. An experienced neurologist can generally distinguish the clinical patterns of sporadic and variant CJD. However, there is some overlap in the symtpoms of the two forms, and, on occasions, it may be difficult to be certain as to the classification of the type of CJD if this were based on the clinical symptoms alone.

Some investigations which are undertaken in CJD may be of great help. In particular, the EEG and the MR scan may be useful. The EEG shows a typical pattern in the majority of cases of sporadic CJD. This typical abnormality has never been seen in variant CJD. The cerebral MRI shows a typical abnormality in the majority of cases of variant CJD which has not been seen in sporadic CJD.

The neuropathological features of variant and sporadic CJD are different. In determining whether an individual has CJD or not, the only absolute test at present is that of neuropathology. Therefore, if an individual has not had neuropathology undertaken on either a brain biopsy in life or at a post mortem, then one cannot be absolutely sure as to the diagnosis. In addition, the neuropathological features of sporadic CJD and variant CJD are quite distinct and this would represent the main definitive method of distinguishing between this two forms of CJD.

There are individuals who do not undergo brain biopsy in life and do not have an autopsy. These individuals may be diagnosed on the basis of "probable sporadic CJD" or "probable variant CJD". Although this does not represent an absolutely definitive diagnosis , if an individual is considered as having "probable" CJD, then it is very likely indeed that this is what they had. Probable sporadic CJD carries a certainty of around 95% or more. To date, all the individuals who have been diagnosed as probable variant in life , who have subsequently had an autopsy have been found to have had variant CJD.