Creutzfeldt-Jakob disease

Creutzfeldt-Jakob disease (CJD) is a rare and fatal form of dementia. It’s caused by a protein found in the brain called a prion. In its natural form, this type of protein is harmless. But in its abnormal form, it’s toxic to brain cells.

There are three major categories of CJD:

1. Sporadic: about 90% of CJD cases fall into this category, and it affects older people, without warning or explanation. The prion protein begins to form in one or a few brain cells and then spreads to the rest of the brain.

2. Genetic prion diseases: about 10% of other CJD cases come from a genetic mutation that can increase your chances of developing the disease. 

3. Transmitted: rarely, the disease can be accidentally transmitted during a medical procedure involving human tissues (“iatrogenic”) or from exposure to cattle (“variant” or BSE, commonly known as mad cow disease).  


It can be several years between when a person is exposed to Creutzfeldt-Jakob disease and the first abnormal prions are formed. Once symptoms take hold, the disease progresses quickly.

CJD affects everyone differently, but eventually the person loses the ability to move, speak and will need full-time care. It’s rare that people with CJD live beyond a year.

Symptoms include:

• loss of memory and thinking abilities (dementia)
• unsteadiness when walking or standing, clumsiness
• sudden jerky movements
• depression, irritability, anxiety, changes in behaviour
• vision problems (including blindness)
• loss of ability to speak or understand speech
• stiffness of arms or legs
• difficulty swallowing
• insomnia (in Fatal familial insomnia)
• persistent pain (in variant CJD) 

More than 50 variations of CJD have been identified, and all of these mutations can have very different symptoms. So can family members who have the same mutation.


Creutzfeldt-Jakob disease is difficult to diagnose, especially in the beginning. However, the following can help detect whether the disease is present:   

Detailed medical history: tells the doctor when the person's signs and symptoms started, because CJD develops so quickly.

Magnetic resonance imaging (MRI): takes a picture of the brain that can show signs of the disease, and tell the difference between sporadic CJD and variant CJD.

Electroencephalogram (EEG): measures the brain’s electrical activity. Often, but not always, there is a specific EEG pattern that helps identify CJD.

Lumbar puncture: cerebrospinal fluid is tested to rule out other infections of the brain. We can also look at certain protein markers that indicate brain cell degeneration, and are higher than normal with CJD.

Blood tests: a sample is often used to prepare DNA, which can be tested to diagnose genetic prion disease.

Brain autopsy: the only definitive way to tell if a person has CJD is to examine the brain tissue in an autopsy.

Risk factors

Sporadic CJD

Sporadic CJD is found worldwide, mostly in people over 50. Canada, the United States, UK, Australia, and several European countries carefully monitor cases of sporadic CJD. About one or two diagnoses typically occur per million people each year.

Genetic prion diseases

Genetic prion diseases mostly affect older people. In some families, the age of onset can be younger and some people with a genetic mutation never develop the illness. The chance that a parent will pass it down is 50% for each child. If a person has a brother or sister with a mutation, there is a 50% chance that they have it too.

Iatrogenic CJD

Most cases of iatrogenic CJD have been found in the United States, UK, France and Japan, with only four cases to date in Canada. Advancements in scientific knowledge and medical technology have greatly reduced the risk of passing CJD from one person to another in this way.

Variant CJD

As of 2016, 231 cases of variant CJD have been reported worldwide, including two in Canadians exposed to BSE while living abroad. The Canadian government has implemented safety measures and regulates the beef industry to minimize the risk of human contact with BSE through food. With these safeguards, the risk of human exposure to BSE is now considered extremely low.


There is no known cure for CJD, no approved medical treatments to prevent it, and no effective way to slow its progression. Care is supportive and focused on keeping the person as comfortable as possible.

For more information:

Creutzfeldt-Jakob disease info sheet, Alzheimer Society of Canada

The latest Canadian statistics:

Last Updated: 05/10/17
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