Page last reviewed: 13/07/2011

Creutzfeldt-Jakob disease (CJD) is a rare neurological illness (disease of the nervous system) that causes damage to the brain. 

It belongs to a group of diseases called transmissible spongiform encephalopathies, or prion diseases, that affect humans and animals.

CJD is fatal and there is no known cure. It is caused by an abnormal protein called a prion, which contaminates the nervous system.


Prions are infectious particles made of abnormally folded protein. In some respects, a prion is similar to a virus as it can replicate and cause disease. But, unlike a virus, it is made entirely from protein and has no genetic material.

This makes prions much tougher than viruses or bacteria. They can survive extremes of heat and radiation and are resistant to being broken down by enzymes, which normally control the body's protein levels. Antibiotic and antiviral medicines have no effect on them.

Prions kill brain cells and make holes in the brain, causing it to become sponge-like. See Causes of CJD for more information.

Types of CJD

There are four different types of CJD, which each have a different cause:

  • Sporadic CJD (sCJD) is the most common form, accounting for 85% of CJD cases.  The cause is unknown, but it normally affects people aged over 40.
  • Variant CJD (vCJD) was first identified in 1996. vCJD is caused by eating meat from cattle infected with BSE (sometimes called mad cow disease). vCJD mainly affects people in their twenties. Most cases occurred in the UK and vCJD is very rare in Ireland. The number of cases in the UK peaked in 2000 and is now declining.
  • Iatrogenic CJD (iCJD) is where the infection is spread from someone with CJD through medical or surgical treatment. Nowadays, cases are extremely rare.
  • Inherited prion disease (IPD) is a rare form of prion disease caused by inheriting a faulty gene that produces prions.

For more information, see Causes of CJD.

All cases of CJD are carefully monitored by the Health Protection Surveillence Centre.


There is no cure for CJD. The condition causes a person to deteriorate rapidly, to the point where they can no longer care for themselves and cannot move or speak.

Most people with sporadic CJD die within six months of diagnosis, often from pneumonia. People with variant CJD live for an average of just over a year.

Page last reviewed: 13/07/2011

The symptoms and course of CJD differ according to the types of CJD and from person to person. However, all four types of CJD share some similar symptoms, which are outlined below.

Early stages

CJD usually starts with emotional or behavioural problems such as depression, anxiety or agitation.

Delusions (strong beliefs in things that are obviously not true) and hallucinations (seeing or hearing things that are not there) are typical of variant CJD.

Patients also develop neurological problems (affecting the nervous system), such as pain or numbness in parts of their body.

Within a few weeks, the person deteriorates rapidly, becoming confused and experiencing memory loss (symptoms typical of dementia).

Later stages

As well as experiencing confusion and memory loss, the person may lose co-ordination and balance and may start to become blind.

Months later, they are unable to walk, speak and care for themselves. They are unaware of their surroundings and usually develop jerking movements of their muscles.

Three-quarters of people with sporadic CJD die within six months of diagnosis, often from pneumonia. Others die within a few weeks. People with variant CJD live for an average of just over a year following diagnosis.

Page last reviewed: 13/07/2011

CJD is caused by an infectious protein in the brain called a prion.

Role of proteins in the brain

Proteins are molecules, made up of amino acids, which help the cells in our body to function.

Proteins begin as a string of amino acids which then fold themselves into a three-dimensional shape. This 'protein folding' allows them to perform useful functions within our cells.

Prion proteins (which are not the same as the infectious prions that cause CJD) are a type of protein found in the brain and several other tissues of the nervous system. The exact role of prion proteins in our brain is unknown, but it is thought they may have something to do with our long-term memory.

When protein folding goes wrong

Sometimes, mistakes happen during protein folding and the prion protein cannot be used by the body. These misfolded prion proteins are normally recycled by the body, but sometimes they can build up. This can cause problems, such as Alzheimer's disease.

Prions are misfolded prion proteins that enter brain cells and cause normal proteins to misfold as well. This causes the brain cell to die, releasing more prions to infect other brain cells.

Eventually, clusters of brain cells are killed and replaced with deposits of prions, called plaques. These plaques produce small holes in the brain, causing it to become sponge-like. The damage to the brain causes the mental and physical impairment and eventual death associated with CJD.

Prions can survive in nerve tissue, such as the brain or spinal cord, for a very long time, even after the person or animal has died.

Sporadic CJD

Sporadic CJD (sCJD) is the most common type of CJD, although it is still very rare. It is not known what triggers sCJD, but it may be due to a normal protein spontaneously changing into a prion or a normal gene spontaneously changing into a faulty gene that produces prions. sCJD normally affects people over 40 years of age.

Variant CJD

There is clear evidence that variant CJD (vCJD) is caused by the same strain of prions that causes bovine spongiform encephalopathy (BSE, also known as mad cow disease).

A UK government inquiry in 2000 concluded that the prion was spread through cattle that were fed meat-and-bone mix containing traces of infected brains or spinal cords. The prion then ended up in processed meat products, such as beefburgers, and entered the human food chain.

Strict controls have been in place in Ireland since 1990, when the feeding of meat and bone mix to cattle was outlawed. The controls were further strengthened in 1996.

Some experts believe that the food controls have worked and that further cases of vCJD will continue to decline.

Other experts have warned that people who have died could have had a genetic trait that meant the vCJD affected them more quickly than normal. Other similar infections caused by prions normally take between 15 and 20 years before they become active. These experts argue that many other people could have vCJD, but the symptoms might not begin to show for many years to come.

Blood transfusions

There have been four cases of variant CJD infection associated with blood transfusion in the UK.  As a result, since the year 2001 ,people who have spent more than 5 years in the UK between 1980 and 1996 have been excluded from giving blood.

Iatrogenic CJD

Iatrogenic CJD (iCJD) is the result of the infection being spread from someone with CJD through medical or surgical treatment.

Most iatrogenic CJD cases have happened through the use of human growth hormone, which is used to treat children who have restricted growth. Between 1958 and 1985, thousands of children were treated with the hormone which, at the time, was extracted from the pituitary glands (a gland that sits at the base of the skull) of human corpses. A tiny minority of those children developed CJD, as the hormones they received were taken from glands infected with CJD. Since 1985, all human growth hormone in Ireland has been artificially manufactured, so there is now no risk.

A few other cases of iCJD occurred when people received transplants of infected tissue or came into contact with surgical instruments that were contaminated with CJD. This happened because prions are tougher than viruses or bacteria, so the normal process of sterilising surgical instruments had no effect.

Once the risk was recognised, the guidelines on organ donation and the reuse of surgical equipment. As a result, cases of iCJD are now extremely rare.

Inherited prion disease

This very rare form of CJD is caused by an inherited mutation (fault) of the gene that produces normal proteins. The altered gene seems to produce prions that cause CJD.

Everyone has two copies of their genes, but the mutated gene is dominant. This means you only need to inherit one mutated gene to develop the illness.

Can CJD be transmitted from person to person?

In theory, CJD can be transmitted from an affected person to others, but only through an injection or consumption of brain tissue.

It is thought that CJD is not spread through ordinary day-to-day contact with those affected or by airborne droplets, blood contact or sexual contact.

Page last reviewed: 13/07/2011

Diagnosis of CJD is normally based on medical history, symptoms and a series of tests (see below). A neurologist (a doctor who specialises in conditions of the nervous system) will carry out the tests to rule out other conditions with similar symptoms, such as Alzheimer's disease, Parkinson's disease or a brain tumour.

The only way to confirm a diagnosis of CJD is to directly examine the brain tissue with a brain biopsy (see below) or, if the person is dead, during a post-mortem.

Checking for common signs of CJD

A clinical neurologist will rule out other diseases with similar symptoms and check for some common signs of CJD by carrying out any of the tests below:

  • magnetic resonance imaging (MRI) brain scan. This uses strong magnetic fields and radio waves to produce a detailed image of the brain and can show up abnormalities that are distinctive to CJD. 
  • An electroencephalogram (EEG). This records brain activity and may pick up abnormal electrical patterns seen in sporadic CJD.
  • A lumbar puncture. A needle is inserted into the lower part of the spine to draw out a sample of cerebrospinal fluid (which surrounds your brain and spinal cord) to be tested. If a protein called 14-3-3 is found in the fluid, it indicates that you may have CJD (this protein is found in almost all cases of sporadic CJD and 50% of variant CJD cases). 
  • Tonsil biopsy. A small piece of tissue can be taken from the tonsils and checked for the abnormal prions found in variant CJD (they are not present in other types of CJD).
  • Genetic test. This is a simple blood test to see if you have a mutation (fault) in the gene that produces normal protein. A positive result may indicate inherited prion disease.

Brain biopsy

During a brain biopsy, a surgeon drills a tiny hole into your skull and removes a small piece of brain tissue using a very thin needle. It is done under general anaesthetic (you are put to sleep).

As a brain biopsy carries the risk of causing brain damage or seizures, it is only performed in a few cases, where there is a concern that the patient does not have CJD but some other treatable condition.


Body tissue is made up of groups of cells that perform a specific job, such as protecting the body against infection, producing movement or storing fat.  
EEG stands for electroencephalogram. It is a painless test that records the electrical messages from the brain.
A biopsy is a test that involves taking a small sample of tissue from the body so it can be examined.
The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.
MRI stands for magnetic resonance imaging. It is the use of magnets and radio waves to take detailed pictures of inside the body.

Page last reviewed: 13/07/2011

There is no proven therapy or cure for any form of CJD.

Treatment involves trying to keep the person as comfortable as possible and reducing symptoms through the use of medicines. For example:

  • Psychological symptoms of CJD, such as anxiety and depression, can be treated with sedatives and antidepressants.
  • Other medicines, such as clonazepam and sodium valproate, can be used to treat muscle jerks and tremors.
  • Opiate-based painkillers can provide effective pain relief.

Specialist team

When somebody is diagnosed with CJD, they will be referred to the appropriate centre for diagnosis and care. A doctor and nurse from these services will be assigned to the patient to liaise with local services, such as the patient's GP, social worker, physiotherapist and occupational therapist.

Specialist teams are available to diagnose and offer clinical and emotional support to patients and their families, and work alongside the local care team. A local care team may include doctors and nurses, occupational therapists, dietitians, incontinence advisers and social workers.

Nursing care and support

As the condition progresses, people with CJD will need significant nursing care and practical support.

As well as help with feeding, washing and mobility, some people may need help with urinating. Often, the use of a catheter (a tube that is inserted into the bladder and used to drain off urine) is required.

Many people will have problems swallowing, so they may have to be given nutrition and fluids through a feeding tube.

It may be possible to treat people with CJD at home, but this will depend on the progression and severity of the condition.

The pressures of caring for someone with CJD can be distressing and difficult to cope with. Rather than coping at home, many carers prefer to use the services of a hospital or hospice.

Page last reviewed: 13/07/2011

Since the link between BSE and CJD was confirmed, strict controls have been in place to stop BSE entering the human food chain. These controls include:

  • a ban on feeding meat-and-bone mix to farm animals
  • the removal and destruction of all parts of an animal's carcass that could be infected with BSE
  • a ban on mechanically recovered meat (meat residue left on the carcass that is pressure-blasted off the bones)
  • testing on all cattle over 30 months old (experience has shown that infection in cattle under 30 months of age is rare, and even cattle that are infected have not yet developed dangerous levels of infection)

Blood transfusions

In the UK, there have been four cases of variant CJD associated with blood transfusions. In each of the cases, the person received a blood transfusion from a donor who later developed variant CJD. These people then went on to develop variant CJD themselves.

It is not certain whether the blood transfusion was the cause of the infection, as the people could have contracted variant CJD through dietary sources. Nevertheless, steps were taken to minimise the risk of the blood supply for transfusion becoming contaminated. These steps include:

  • not allowing people potentially at risk from CJD to donate blood, tissue or organs
  • not accepting donations from people who have received a blood transfusion in the UK since 1980
  • removing white blood cells, which may carry the greatest risk of transmitting CJD, from all blood used for transfusions

Content provided by NHS Choices and adapted for Ireland by the Health A-Z.

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